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	$174.82	8.308%	$189.344	$189.34	$189.35	$189.30
Purchase #2	$173.37	9.482%	$189.8089	$189.81	$189.80	$189.80
Purchase #3	$129.59	3.357%	$133.9403	$133.94	$133.95	$133.90
Purchase #4	$18.39	11.265%	$20.4616	$20.46	$20.45	$20.50
Purchase #5	$209.65	9.366%	$229.2858	$229.29	$229.30	$229.30
Purchase #6	$68.70	5.543%	$72.508	$72.51	$72.50	$72.50
Purchase #7	$83.77	8.789%	$91.1325	$91.13	$91.15	$91.10
7 purchase totals =	$858.29		$926.4811	$926.48	$926.50	$926.40