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	$169.36	11.512%	$188.8567	$188.86	$188.85	$188.90
Purchase #2	$172.48	4.199%	$179.7224	$179.72	$179.70	$179.70
Purchase #3	$57.36	7.179%	$61.4779	$61.48	$61.50	$61.50
Purchase #4	$31.54	12.871%	$35.5995	$35.60	$35.60	$35.60
Purchase #5	$150.87	5.476%	$159.1316	$159.13	$159.15	$159.10
Purchase #6	$82.79	7.533%	$89.0266	$89.03	$89.05	$89.00
Purchase #7	$211.64	8.427%	$229.4749	$229.47	$229.45	$229.50
7 purchase totals =	$876.04		$943.2896	$943.29	$943.30	$943.30