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	$105.85	12.357%	$118.9299	$118.93	$118.95	$118.90
Purchase #2	$62.52	5.462%	$65.9348	$65.93	$65.95	$65.90
Purchase #3	$82.84	3.581%	$85.8065	$85.81	$85.80	$85.80
Purchase #4	$236.88	5.775%	$250.5598	$250.56	$250.55	$250.60
Purchase #5	$171.97	7.263%	$184.4602	$184.46	$184.45	$184.50
Purchase #6	$50.37	9.833%	$55.3229	$55.32	$55.30	$55.30
Purchase #7	$149.76	3.814%	$155.4718	$155.47	$155.45	$155.50
7 purchase totals =	$860.19		$916.4859	$916.48	$916.45	$916.50