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	$90.85	7.504%	$97.6674	$97.67	$97.65	$97.70
Purchase #2	$68.56	8.306%	$74.2546	$74.25	$74.25	$74.30
Purchase #3	$125.29	4.804%	$131.3089	$131.31	$131.30	$131.30
Purchase #4	$27.29	10.492%	$30.1533	$30.15	$30.15	$30.20
Purchase #5	$224.74	10.590%	$248.54	$248.54	$248.55	$248.50
Purchase #6	$72.55	13.488%	$82.3355	$82.34	$82.35	$82.30
Purchase #7	$66.90	7.480%	$71.9041	$71.90	$71.90	$71.90
7 purchase totals =	$676.18		$736.1638	$736.16	$736.15	$736.20