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	$212.66	5.229%	$223.78	$223.78	$223.80	$223.80
Purchase #2	$98.85	5.439%	$104.2265	$104.23	$104.25	$104.20
Purchase #3	$47.59	12.502%	$53.5397	$53.54	$53.55	$53.50
Purchase #4	$236.64	5.422%	$249.4706	$249.47	$249.45	$249.50
Purchase #5	$146.40	12.388%	$164.536	$164.54	$164.55	$164.50
Purchase #6	$159.40	8.442%	$172.8565	$172.86	$172.85	$172.90
Purchase #7	$146.96	9.483%	$160.8962	$160.90	$160.90	$160.90
7 purchase totals =	$1,048.50		$1,129.3055	$1,129.32	$1,129.35	$1,129.30