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	$232.75	3.863%	$241.7411	$241.74	$241.75	$241.70
Purchase #2	$91.72	7.838%	$98.909	$98.91	$98.90	$98.90
Purchase #3	$106.67	12.384%	$119.88	$119.88	$119.90	$119.90
Purchase #4	$151.72	6.228%	$161.1691	$161.17	$161.15	$161.20
Purchase #5	$163.74	7.136%	$175.4245	$175.42	$175.40	$175.40
Purchase #6	$92.89	5.753%	$98.234	$98.23	$98.25	$98.20
Purchase #7	$240.41	6.404%	$255.8059	$255.81	$255.80	$255.80
7 purchase totals =	$1,079.90		$1,151.1636	$1,151.16	$1,151.15	$1,151.10