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	$213.60	3.525%	$221.1294	$221.13	$221.15	$221.10
Purchase #2	$110.45	9.794%	$121.2675	$121.27	$121.25	$121.30
Purchase #3	$240.86	4.163%	$250.887	$250.89	$250.90	$250.90
Purchase #4	$52.91	12.159%	$59.3433	$59.34	$59.35	$59.30
Purchase #5	$110.27	12.444%	$123.992	$123.99	$124.00	$124.00
Purchase #6	$106.87	4.596%	$111.7817	$111.78	$111.80	$111.80
Purchase #7	$25.34	3.462%	$26.2173	$26.22	$26.20	$26.20
7 purchase totals =	$860.30		$914.6182	$914.62	$914.65	$914.60