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	$47.31	10.359%	$52.2108	$52.21	$52.20	$52.20
Purchase #2	$208.82	5.196%	$219.6703	$219.67	$219.65	$219.70
Purchase #3	$36.49	8.208%	$39.4851	$39.49	$39.50	$39.50
Purchase #4	$165.32	13.340%	$187.3737	$187.37	$187.35	$187.40
Purchase #5	$209.90	10.823%	$232.6175	$232.62	$232.60	$232.60
Purchase #6	$17.27	7.386%	$18.5456	$18.55	$18.55	$18.50
Purchase #7	$248.82	8.303%	$269.4795	$269.48	$269.50	$269.50
7 purchase totals =	$933.93		$1,019.3825	$1,019.39	$1,019.35	$1,019.40