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	$226.70	13.140%	$256.4884	$256.49	$256.50	$256.50
Purchase #2	$54.63	13.336%	$61.9155	$61.92	$61.90	$61.90
Purchase #3	$78.64	13.254%	$89.0629	$89.06	$89.05	$89.10
Purchase #4	$163.29	3.541%	$169.0721	$169.07	$169.05	$169.10
Purchase #5	$186.55	3.279%	$192.667	$192.67	$192.65	$192.70
Purchase #6	$41.74	4.213%	$43.4985	$43.50	$43.50	$43.50
Purchase #7	$182.61	12.465%	$205.3723	$205.37	$205.35	$205.40
7 purchase totals =	$934.16		$1,018.0767	$1,018.08	$1,018.00	$1,018.20