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	$120.57	3.812%	$125.1661	$125.17	$125.15	$125.20
Purchase #2	$126.67	4.324%	$132.1472	$132.15	$132.15	$132.10
Purchase #3	$72.25	10.567%	$79.8847	$79.88	$79.90	$79.90
Purchase #4	$132.34	13.843%	$150.6598	$150.66	$150.65	$150.70
Purchase #5	$20.89	6.414%	$22.2299	$22.23	$22.25	$22.20
Purchase #6	$53.90	3.667%	$55.8765	$55.88	$55.90	$55.90
Purchase #7	$98.76	6.803%	$105.4786	$105.48	$105.50	$105.50
7 purchase totals =	$625.38		$671.4428	$671.45	$671.50	$671.50