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	$145.31	3.571%	$150.499	$150.50	$150.50	$150.50
Purchase #2	$80.41	6.325%	$85.4959	$85.50	$85.50	$85.50
Purchase #3	$217.91	13.415%	$247.1426	$247.14	$247.15	$247.10
Purchase #4	$95.38	4.248%	$99.4317	$99.43	$99.45	$99.40
Purchase #5	$35.80	13.242%	$40.5406	$40.54	$40.55	$40.50
Purchase #6	$128.84	8.449%	$139.7257	$139.73	$139.75	$139.70
Purchase #7	$95.99	6.113%	$101.8579	$101.86	$101.85	$101.90
7 purchase totals =	$799.64		$864.6934	$864.70	$864.75	$864.60