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	$209.45	5.786%	$221.5688	$221.57	$221.55	$221.60
Purchase #2	$160.27	6.608%	$170.8606	$170.86	$170.85	$170.90
Purchase #3	$22.96	13.355%	$26.0263	$26.03	$26.05	$26.00
Purchase #4	$149.82	12.139%	$168.0066	$168.01	$168.00	$168.00
Purchase #5	$78.32	6.784%	$83.6332	$83.63	$83.65	$83.60
Purchase #6	$118.89	10.344%	$131.188	$131.19	$131.20	$131.20
Purchase #7	$104.33	8.181%	$112.8652	$112.87	$112.85	$112.90
7 purchase totals =	$844.04		$914.1487	$914.16	$914.15	$914.20