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	$169.53	9.389%	$185.4472	$185.45	$185.45	$185.40
Purchase #2	$35.73	10.828%	$39.5988	$39.60	$39.60	$39.60
Purchase #3	$184.56	12.843%	$208.263	$208.26	$208.25	$208.30
Purchase #4	$46.89	7.338%	$50.3308	$50.33	$50.35	$50.30
Purchase #5	$211.45	10.505%	$233.6628	$233.66	$233.65	$233.70
Purchase #6	$189.65	13.663%	$215.5619	$215.56	$215.55	$215.60
Purchase #7	$133.42	5.705%	$141.0316	$141.03	$141.05	$141.00
7 purchase totals =	$971.23		$1,073.8961	$1,073.89	$1,073.90	$1,073.90