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	$201.34	4.830%	$211.0647	$211.06	$211.05	$211.10
Purchase #2	$18.97	11.653%	$21.1806	$21.18	$21.20	$21.20
Purchase #3	$137.49	10.214%	$151.5332	$151.53	$151.55	$151.50
Purchase #4	$129.55	10.442%	$143.0776	$143.08	$143.10	$143.10
Purchase #5	$94.90	10.750%	$105.1018	$105.10	$105.10	$105.10
Purchase #6	$222.45	11.188%	$247.3377	$247.34	$247.35	$247.30
Purchase #7	$216.38	6.246%	$229.8951	$229.90	$229.90	$229.90
7 purchase totals =	$1,021.08		$1,109.1907	$1,109.19	$1,109.25	$1,109.20