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	$71.38	9.560%	$78.2039	$78.20	$78.20	$78.20
Purchase #2	$91.75	8.159%	$99.2359	$99.24	$99.25	$99.20
Purchase #3	$83.29	13.442%	$94.4858	$94.49	$94.50	$94.50
Purchase #4	$227.88	12.450%	$256.2511	$256.25	$256.25	$256.30
Purchase #5	$139.83	6.749%	$149.2671	$149.27	$149.25	$149.30
Purchase #6	$232.32	6.517%	$247.4603	$247.46	$247.45	$247.50
Purchase #7	$13.50	9.445%	$14.7751	$14.78	$14.80	$14.80
7 purchase totals =	$859.95		$939.6792	$939.69	$939.70	$939.80