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	$247.51	3.502%	$256.1778	$256.18	$256.20	$256.20
Purchase #2	$166.73	13.872%	$189.8588	$189.86	$189.85	$189.90
Purchase #3	$12.61	3.495%	$13.0507	$13.05	$13.05	$13.10
Purchase #4	$60.78	7.272%	$65.1999	$65.20	$65.20	$65.20
Purchase #5	$233.64	9.361%	$255.511	$255.51	$255.50	$255.50
Purchase #6	$181.44	3.720%	$188.1896	$188.19	$188.20	$188.20
Purchase #7	$58.29	7.775%	$62.822	$62.82	$62.80	$62.80
7 purchase totals =	$961.00		$1,030.8098	$1,030.81	$1,030.80	$1,030.90