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	$172.93	9.158%	$188.7669	$188.77	$188.75	$188.80
Purchase #2	$144.81	12.486%	$162.891	$162.89	$162.90	$162.90
Purchase #3	$217.84	7.168%	$233.4548	$233.45	$233.45	$233.50
Purchase #4	$160.94	9.693%	$176.5399	$176.54	$176.55	$176.50
Purchase #5	$82.49	13.309%	$93.4686	$93.47	$93.45	$93.50
Purchase #6	$111.86	11.244%	$124.4375	$124.44	$124.45	$124.40
Purchase #7	$57.32	7.807%	$61.795	$61.80	$61.80	$61.80
7 purchase totals =	$948.19		$1,041.3537	$1,041.36	$1,041.35	$1,041.40