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	$154.63	12.715%	$174.2912	$174.29	$174.30	$174.30
Purchase #2	$132.48	7.634%	$142.5935	$142.59	$142.60	$142.60
Purchase #3	$248.94	11.474%	$277.5034	$277.50	$277.50	$277.50
Purchase #4	$110.58	5.684%	$116.8654	$116.87	$116.85	$116.90
Purchase #5	$139.90	4.532%	$146.2403	$146.24	$146.25	$146.20
Purchase #6	$139.60	6.455%	$148.6112	$148.61	$148.60	$148.60
Purchase #7	$55.88	11.260%	$62.1721	$62.17	$62.15	$62.20
7 purchase totals =	$982.01		$1,068.2771	$1,068.27	$1,068.25	$1,068.30