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	$151.54	9.261%	$165.5741	$165.57	$165.55	$165.60
Purchase #2	$85.37	6.350%	$90.791	$90.79	$90.80	$90.80
Purchase #3	$221.59	10.139%	$244.057	$244.06	$244.05	$244.10
Purchase #4	$205.69	3.682%	$213.2635	$213.26	$213.25	$213.30
Purchase #5	$61.58	7.796%	$66.3808	$66.38	$66.40	$66.40
Purchase #6	$186.89	4.506%	$195.3113	$195.31	$195.30	$195.30
Purchase #7	$66.27	7.572%	$71.288	$71.29	$71.30	$71.30
7 purchase totals =	$978.93		$1,046.6657	$1,046.66	$1,046.65	$1,046.80