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	$175.30	8.370%	$189.9726	$189.97	$189.95	$190.00
Purchase #2	$81.51	11.378%	$90.7842	$90.78	$90.80	$90.80
Purchase #3	$52.89	10.693%	$58.5455	$58.55	$58.55	$58.50
Purchase #4	$95.27	6.831%	$101.7779	$101.78	$101.80	$101.80
Purchase #5	$118.80	11.505%	$132.4679	$132.47	$132.45	$132.50
Purchase #6	$250.49	5.650%	$264.6427	$264.64	$264.65	$264.60
Purchase #7	$193.54	9.614%	$212.1469	$212.15	$212.15	$212.10
7 purchase totals =	$967.80		$1,050.3377	$1,050.34	$1,050.35	$1,050.30