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	$105.89	13.132%	$119.7955	$119.80	$119.80	$119.80
Purchase #2	$134.42	9.772%	$147.5555	$147.56	$147.55	$147.60
Purchase #3	$189.31	5.202%	$199.1579	$199.16	$199.15	$199.20
Purchase #4	$123.41	7.602%	$132.7916	$132.79	$132.80	$132.80
Purchase #5	$175.95	11.648%	$196.4447	$196.44	$196.45	$196.40
Purchase #6	$108.56	9.653%	$119.0393	$119.04	$119.05	$119.00
Purchase #7	$47.87	4.695%	$50.1175	$50.12	$50.10	$50.10
7 purchase totals =	$885.41		$964.9020	$964.91	$964.90	$964.90