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	$177.47	10.757%	$196.5604	$196.56	$196.55	$196.60
Purchase #2	$40.42	8.728%	$43.9479	$43.95	$43.95	$43.90
Purchase #3	$48.38	5.131%	$50.8624	$50.86	$50.85	$50.90
Purchase #4	$155.58	9.345%	$170.119	$170.12	$170.10	$170.10
Purchase #5	$135.98	8.426%	$147.4377	$147.44	$147.45	$147.40
Purchase #6	$65.40	10.435%	$72.2245	$72.22	$72.20	$72.20
Purchase #7	$184.87	3.706%	$191.7213	$191.72	$191.70	$191.70
7 purchase totals =	$808.10		$872.8732	$872.87	$872.80	$872.80