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	$10.25	10.762%	$11.3531	$11.35	$11.35	$11.40
Purchase #2	$159.44	12.457%	$179.3014	$179.30	$179.30	$179.30
Purchase #3	$239.66	10.788%	$265.5145	$265.51	$265.50	$265.50
Purchase #4	$90.50	7.572%	$97.3527	$97.35	$97.35	$97.40
Purchase #5	$175.64	8.131%	$189.9213	$189.92	$189.90	$189.90
Purchase #6	$230.77	7.811%	$248.7954	$248.80	$248.80	$248.80
Purchase #7	$53.29	7.861%	$57.4791	$57.48	$57.50	$57.50
7 purchase totals =	$959.55		$1,049.7175	$1,049.71	$1,049.70	$1,049.80