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	$213.69	7.406%	$229.5159	$229.52	$229.50	$229.50
Purchase #2	$74.82	4.415%	$78.1233	$78.12	$78.10	$78.10
Purchase #3	$145.49	13.718%	$165.4483	$165.45	$165.45	$165.40
Purchase #4	$183.29	9.500%	$200.7026	$200.70	$200.70	$200.70
Purchase #5	$131.77	7.122%	$141.1547	$141.15	$141.15	$141.20
Purchase #6	$13.90	13.849%	$15.825	$15.83	$15.85	$15.80
Purchase #7	$62.96	6.636%	$67.138	$67.14	$67.15	$67.10
7 purchase totals =	$825.92		$897.9078	$897.91	$897.90	$897.80