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	$89.92	3.871%	$93.4008	$93.40	$93.40	$93.40
Purchase #2	$179.83	3.249%	$185.6727	$185.67	$185.65	$185.70
Purchase #3	$31.26	10.713%	$34.6089	$34.61	$34.60	$34.60
Purchase #4	$180.79	4.635%	$189.1696	$189.17	$189.15	$189.20
Purchase #5	$244.98	3.586%	$253.765	$253.77	$253.75	$253.80
Purchase #6	$239.49	6.641%	$255.3945	$255.39	$255.40	$255.40
Purchase #7	$108.73	10.286%	$119.914	$119.91	$119.90	$119.90
7 purchase totals =	$1,075.00		$1,131.9255	$1,131.92	$1,131.85	$1,132.00