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	$116.62	5.801%	$123.3851	$123.39	$123.40	$123.40
Purchase #2	$173.33	6.172%	$184.0279	$184.03	$184.05	$184.00
Purchase #3	$163.57	3.640%	$169.5239	$169.52	$169.50	$169.50
Purchase #4	$31.42	5.551%	$33.1641	$33.16	$33.15	$33.20
Purchase #5	$188.85	4.231%	$196.8402	$196.84	$196.85	$196.80
Purchase #6	$218.28	12.165%	$244.8338	$244.83	$244.85	$244.80
Purchase #7	$223.50	4.547%	$233.6625	$233.66	$233.65	$233.70
7 purchase totals =	$1,115.57		$1,185.4375	$1,185.43	$1,185.45	$1,185.40