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	$222.43	4.445%	$232.317	$232.32	$232.30	$232.30
Purchase #2	$136.67	7.223%	$146.5417	$146.54	$146.55	$146.50
Purchase #3	$203.86	11.296%	$226.888	$226.89	$226.90	$226.90
Purchase #4	$43.59	4.308%	$45.4679	$45.47	$45.45	$45.50
Purchase #5	$22.29	13.695%	$25.3426	$25.34	$25.35	$25.30
Purchase #6	$85.53	4.297%	$89.2052	$89.21	$89.20	$89.20
Purchase #7	$161.74	10.272%	$178.3539	$178.35	$178.35	$178.40
7 purchase totals =	$876.11		$944.1163	$944.12	$944.10	$944.10