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	$100.34	3.744%	$104.0967	$104.10	$104.10	$104.10
Purchase #2	$34.51	10.223%	$38.038	$38.04	$38.05	$38.00
Purchase #3	$203.91	9.114%	$222.4944	$222.49	$222.50	$222.50
Purchase #4	$81.62	11.360%	$90.892	$90.89	$90.90	$90.90
Purchase #5	$55.31	9.461%	$60.5429	$60.54	$60.55	$60.50
Purchase #6	$19.94	7.610%	$21.4574	$21.46	$21.45	$21.50
Purchase #7	$157.27	10.362%	$173.5663	$173.57	$173.55	$173.60
7 purchase totals =	$652.90		$711.0877	$711.09	$711.10	$711.10