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	$65.39	3.127%	$67.4347	$67.43	$67.45	$67.40
Purchase #2	$160.61	11.395%	$178.9115	$178.91	$178.90	$178.90
Purchase #3	$222.89	5.477%	$235.0977	$235.10	$235.10	$235.10
Purchase #4	$36.38	8.580%	$39.5014	$39.50	$39.50	$39.50
Purchase #5	$47.33	13.407%	$53.6755	$53.68	$53.70	$53.70
Purchase #6	$245.74	7.836%	$264.9962	$265.00	$265.00	$265.00
Purchase #7	$155.81	6.447%	$165.8551	$165.86	$165.85	$165.90
7 purchase totals =	$934.15		$1,005.4721	$1,005.48	$1,005.50	$1,005.50