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	$67.40	13.520%	$76.5125	$76.51	$76.50	$76.50
Purchase #2	$208.76	4.254%	$217.6407	$217.64	$217.65	$217.60
Purchase #3	$160.30	4.872%	$168.1098	$168.11	$168.10	$168.10
Purchase #4	$162.74	6.351%	$173.0756	$173.08	$173.10	$173.10
Purchase #5	$86.91	3.679%	$90.1074	$90.11	$90.10	$90.10
Purchase #6	$130.29	13.741%	$148.1931	$148.19	$148.20	$148.20
Purchase #7	$79.91	13.346%	$90.5748	$90.57	$90.55	$90.60
7 purchase totals =	$896.31		$964.2139	$964.21	$964.20	$964.20