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	$169.67	7.539%	$182.4614	$182.46	$182.45	$182.50
Purchase #2	$61.68	7.343%	$66.2092	$66.21	$66.20	$66.20
Purchase #3	$32.31	3.707%	$33.5077	$33.51	$33.50	$33.50
Purchase #4	$44.74	12.653%	$50.401	$50.40	$50.40	$50.40
Purchase #5	$83.27	7.262%	$89.3171	$89.32	$89.30	$89.30
Purchase #6	$161.90	5.404%	$170.6491	$170.65	$170.65	$170.60
Purchase #7	$93.58	5.746%	$98.9571	$98.96	$98.95	$99.00
7 purchase totals =	$647.15		$691.5026	$691.51	$691.45	$691.50