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	$126.40	13.706%	$143.7244	$143.72	$143.70	$143.70
Purchase #2	$46.79	9.702%	$51.3296	$51.33	$51.35	$51.30
Purchase #3	$121.40	7.406%	$130.3909	$130.39	$130.40	$130.40
Purchase #4	$136.44	13.634%	$155.0422	$155.04	$155.05	$155.00
Purchase #5	$221.59	7.735%	$238.73	$238.73	$238.75	$238.70
Purchase #6	$73.98	5.642%	$78.154	$78.15	$78.15	$78.20
Purchase #7	$132.31	7.280%	$141.9422	$141.94	$141.95	$141.90
7 purchase totals =	$858.91		$939.3133	$939.30	$939.35	$939.20