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	$62.70	7.484%	$67.3925	$67.39	$67.40	$67.40
Purchase #2	$73.88	5.834%	$78.1902	$78.19	$78.20	$78.20
Purchase #3	$153.82	10.318%	$169.6911	$169.69	$169.70	$169.70
Purchase #4	$98.90	12.272%	$111.037	$111.04	$111.05	$111.00
Purchase #5	$71.94	12.383%	$80.8483	$80.85	$80.85	$80.80
Purchase #6	$191.32	3.657%	$198.3166	$198.32	$198.30	$198.30
Purchase #7	$31.35	4.719%	$32.8294	$32.83	$32.85	$32.80
7 purchase totals =	$683.91		$738.3051	$738.31	$738.35	$738.20