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	$24.86	4.150%	$25.8917	$25.89	$25.90	$25.90
Purchase #2	$86.52	3.640%	$89.6693	$89.67	$89.65	$89.70
Purchase #3	$155.52	6.421%	$165.5059	$165.51	$165.50	$165.50
Purchase #4	$110.48	7.662%	$118.945	$118.95	$118.95	$118.90
Purchase #5	$56.80	6.575%	$60.5346	$60.53	$60.55	$60.50
Purchase #6	$76.30	4.748%	$79.9227	$79.92	$79.90	$79.90
Purchase #7	$153.51	11.256%	$170.7891	$170.79	$170.80	$170.80
7 purchase totals =	$663.99		$711.2583	$711.26	$711.25	$711.20