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	$88.91	6.264%	$94.4793	$94.48	$94.50	$94.50
Purchase #2	$60.75	6.484%	$64.689	$64.69	$64.70	$64.70
Purchase #3	$239.77	5.787%	$253.6455	$253.65	$253.65	$253.60
Purchase #4	$41.60	7.227%	$44.6064	$44.61	$44.60	$44.60
Purchase #5	$98.52	13.597%	$111.9158	$111.92	$111.90	$111.90
Purchase #6	$248.88	8.241%	$269.3902	$269.39	$269.40	$269.40
Purchase #7	$113.91	8.316%	$123.3828	$123.38	$123.40	$123.40
7 purchase totals =	$892.34		$962.1090	$962.12	$962.15	$962.10