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	$174.76	12.326%	$196.3009	$196.30	$196.30	$196.30
Purchase #2	$40.95	4.691%	$42.871	$42.87	$42.85	$42.90
Purchase #3	$220.78	12.263%	$247.8543	$247.85	$247.85	$247.90
Purchase #4	$242.32	8.449%	$262.7936	$262.79	$262.80	$262.80
Purchase #5	$128.33	7.199%	$137.5685	$137.57	$137.55	$137.60
Purchase #6	$164.86	12.723%	$185.8351	$185.84	$185.85	$185.80
Purchase #7	$160.71	9.236%	$175.5532	$175.55	$175.55	$175.60
7 purchase totals =	$1,132.71		$1,248.7766	$1,248.77	$1,248.75	$1,248.90