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	$195.41	8.580%	$212.1762	$212.18	$212.20	$212.20
Purchase #2	$59.53	13.494%	$67.563	$67.56	$67.55	$67.60
Purchase #3	$173.54	12.590%	$195.3887	$195.39	$195.40	$195.40
Purchase #4	$84.76	9.603%	$92.8995	$92.90	$92.90	$92.90
Purchase #5	$7.74	9.275%	$8.4579	$8.46	$8.45	$8.50
Purchase #6	$79.90	12.513%	$89.8979	$89.90	$89.90	$89.90
Purchase #7	$146.82	8.582%	$159.4201	$159.42	$159.40	$159.40
7 purchase totals =	$747.70		$825.8033	$825.81	$825.80	$825.90