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	$124.31	6.388%	$132.2509	$132.25	$132.25	$132.30
Purchase #2	$43.71	6.486%	$46.545	$46.55	$46.55	$46.50
Purchase #3	$227.71	13.618%	$258.7195	$258.72	$258.70	$258.70
Purchase #4	$187.84	4.634%	$196.5445	$196.54	$196.55	$196.50
Purchase #5	$166.50	11.840%	$186.2136	$186.21	$186.20	$186.20
Purchase #6	$29.41	10.606%	$32.5292	$32.53	$32.55	$32.50
Purchase #7	$250.53	4.803%	$262.563	$262.56	$262.55	$262.60
7 purchase totals =	$1,030.01		$1,115.3657	$1,115.36	$1,115.35	$1,115.30