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	$111.69	7.475%	$120.0388	$120.04	$120.05	$120.00
Purchase #2	$62.97	4.574%	$65.8502	$65.85	$65.85	$65.90
Purchase #3	$156.97	5.691%	$165.9032	$165.90	$165.90	$165.90
Purchase #4	$147.38	4.706%	$154.3157	$154.32	$154.30	$154.30
Purchase #5	$88.30	8.118%	$95.4682	$95.47	$95.45	$95.50
Purchase #6	$219.66	11.500%	$244.9209	$244.92	$244.90	$244.90
Purchase #7	$195.82	11.132%	$217.6187	$217.62	$217.60	$217.60
7 purchase totals =	$982.79		$1,064.1157	$1,064.12	$1,064.05	$1,064.10