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	$218.89	11.743%	$244.5943	$244.59	$244.60	$244.60
Purchase #2	$178.68	10.105%	$196.7356	$196.74	$196.75	$196.70
Purchase #3	$18.95	6.701%	$20.2198	$20.22	$20.20	$20.20
Purchase #4	$210.55	11.205%	$234.1421	$234.14	$234.15	$234.10
Purchase #5	$164.98	8.676%	$179.2937	$179.29	$179.30	$179.30
Purchase #6	$122.79	11.681%	$137.1331	$137.13	$137.15	$137.10
Purchase #7	$136.30	12.404%	$153.2067	$153.21	$153.20	$153.20
7 purchase totals =	$1,051.14		$1,165.3253	$1,165.32	$1,165.35	$1,165.20