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	$132.55	11.312%	$147.5441	$147.54	$147.55	$147.50
Purchase #2	$166.95	9.181%	$182.2777	$182.28	$182.30	$182.30
Purchase #3	$235.64	8.360%	$255.3395	$255.34	$255.35	$255.30
Purchase #4	$9.60	10.622%	$10.6197	$10.62	$10.60	$10.60
Purchase #5	$120.48	6.326%	$128.1016	$128.10	$128.10	$128.10
Purchase #6	$217.53	6.385%	$231.4193	$231.42	$231.40	$231.40
Purchase #7	$71.32	11.600%	$79.5931	$79.59	$79.60	$79.60
7 purchase totals =	$954.07		$1,034.8950	$1,034.89	$1,034.90	$1,034.80