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	$188.75	13.332%	$213.9142	$213.91	$213.90	$213.90
Purchase #2	$103.41	6.507%	$110.1389	$110.14	$110.15	$110.10
Purchase #3	$82.86	8.348%	$89.7772	$89.78	$89.80	$89.80
Purchase #4	$89.42	12.394%	$100.5027	$100.50	$100.50	$100.50
Purchase #5	$203.95	7.455%	$219.1545	$219.15	$219.15	$219.20
Purchase #6	$222.39	12.664%	$250.5535	$250.55	$250.55	$250.60
Purchase #7	$37.85	7.518%	$40.6956	$40.70	$40.70	$40.70
7 purchase totals =	$928.63		$1,024.7366	$1,024.73	$1,024.75	$1,024.80