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	$148.48	11.301%	$165.2597	$165.26	$165.25	$165.30
Purchase #2	$225.81	5.767%	$238.8325	$238.83	$238.85	$238.80
Purchase #3	$39.89	8.795%	$43.3983	$43.40	$43.40	$43.40
Purchase #4	$64.50	4.263%	$67.2496	$67.25	$67.25	$67.20
Purchase #5	$151.69	10.841%	$168.1347	$168.13	$168.15	$168.10
Purchase #6	$89.50	4.609%	$93.6251	$93.63	$93.65	$93.60
Purchase #7	$7.90	9.643%	$8.6618	$8.66	$8.65	$8.70
7 purchase totals =	$727.77		$785.1617	$785.16	$785.20	$785.10