Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$240.32	12.150%	$269.5189	$269.52	$269.50	$269.50
Purchase #2	$178.73	10.776%	$197.9899	$197.99	$198.00	$198.00
Purchase #3	$172.42	10.551%	$190.612	$190.61	$190.60	$190.60
Purchase #4	$108.99	5.813%	$115.3256	$115.33	$115.35	$115.30
Purchase #5	$112.58	10.821%	$124.7623	$124.76	$124.75	$124.80
Purchase #6	$105.36	3.693%	$109.2509	$109.25	$109.25	$109.30
Purchase #7	$173.42	9.213%	$189.3972	$189.40	$189.40	$189.40
7 purchase totals =	$1,091.82		$1,196.8568	$1,196.86	$1,196.85	$1,196.90