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	$75.27	11.114%	$83.6355	$83.64	$83.65	$83.60
Purchase #2	$138.65	6.286%	$147.3655	$147.37	$147.35	$147.40
Purchase #3	$101.48	10.223%	$111.8543	$111.85	$111.85	$111.90
Purchase #4	$149.32	13.564%	$169.5738	$169.57	$169.55	$169.60
Purchase #5	$109.31	12.182%	$122.6261	$122.63	$122.65	$122.60
Purchase #6	$192.60	3.614%	$199.5606	$199.56	$199.55	$199.60
Purchase #7	$209.25	6.465%	$222.778	$222.78	$222.80	$222.80
7 purchase totals =	$975.88		$1,057.3938	$1,057.40	$1,057.40	$1,057.50