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	$223.94	9.108%	$244.3365	$244.34	$244.35	$244.30
Purchase #2	$119.79	9.219%	$130.8334	$130.83	$130.85	$130.80
Purchase #3	$216.52	3.401%	$223.8838	$223.88	$223.90	$223.90
Purchase #4	$124.54	11.640%	$139.0365	$139.04	$139.05	$139.00
Purchase #5	$210.40	11.728%	$235.0757	$235.08	$235.10	$235.10
Purchase #6	$91.44	10.115%	$100.6892	$100.69	$100.70	$100.70
Purchase #7	$6.51	9.835%	$7.1503	$7.15	$7.15	$7.20
7 purchase totals =	$993.14		$1,081.0054	$1,081.01	$1,081.10	$1,081.00