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	$211.52	3.399%	$218.7096	$218.71	$218.70	$218.70
Purchase #2	$33.94	9.179%	$37.0554	$37.06	$37.05	$37.10
Purchase #3	$152.87	10.200%	$168.4627	$168.46	$168.45	$168.50
Purchase #4	$98.77	12.649%	$111.2634	$111.26	$111.25	$111.30
Purchase #5	$206.29	5.831%	$218.3188	$218.32	$218.30	$218.30
Purchase #6	$135.30	8.507%	$146.81	$146.81	$146.80	$146.80
Purchase #7	$219.29	5.397%	$231.1251	$231.13	$231.15	$231.10
7 purchase totals =	$1,057.98		$1,131.7450	$1,131.75	$1,131.70	$1,131.80