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	$33.69	5.592%	$35.5739	$35.57	$35.55	$35.60
Purchase #2	$16.73	6.238%	$17.7736	$17.77	$17.75	$17.80
Purchase #3	$141.87	5.826%	$150.1353	$150.14	$150.15	$150.10
Purchase #4	$11.80	9.226%	$12.8887	$12.89	$12.90	$12.90
Purchase #5	$126.82	9.180%	$138.4621	$138.46	$138.45	$138.50
Purchase #6	$77.84	9.329%	$85.1017	$85.10	$85.10	$85.10
Purchase #7	$37.73	12.594%	$42.4817	$42.48	$42.50	$42.50
7 purchase totals =	$446.48		$482.4170	$482.41	$482.40	$482.50