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	$167.88	7.356%	$180.2293	$180.23	$180.25	$180.20
Purchase #2	$181.46	7.656%	$195.3526	$195.35	$195.35	$195.40
Purchase #3	$77.32	7.256%	$82.9303	$82.93	$82.95	$82.90
Purchase #4	$143.41	10.561%	$158.5555	$158.56	$158.55	$158.60
Purchase #5	$110.96	12.517%	$124.8489	$124.85	$124.85	$124.80
Purchase #6	$37.71	8.825%	$41.0379	$41.04	$41.05	$41.00
Purchase #7	$82.87	3.389%	$85.6785	$85.68	$85.70	$85.70
7 purchase totals =	$801.61		$868.6330	$868.64	$868.70	$868.60