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	$236.69	11.648%	$264.2597	$264.26	$264.25	$264.30
Purchase #2	$209.87	11.208%	$233.3922	$233.39	$233.40	$233.40
Purchase #3	$89.76	3.301%	$92.723	$92.72	$92.70	$92.70
Purchase #4	$210.95	12.414%	$237.1373	$237.14	$237.15	$237.10
Purchase #5	$206.97	4.438%	$216.1553	$216.16	$216.15	$216.20
Purchase #6	$145.88	4.446%	$152.3658	$152.37	$152.35	$152.40
Purchase #7	$109.33	8.369%	$118.4798	$118.48	$118.50	$118.50
7 purchase totals =	$1,209.45		$1,314.5131	$1,314.52	$1,314.50	$1,314.60