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	$105.29	3.650%	$109.1331	$109.13	$109.15	$109.10
Purchase #2	$33.81	6.729%	$36.0851	$36.09	$36.10	$36.10
Purchase #3	$207.79	10.615%	$229.8469	$229.85	$229.85	$229.80
Purchase #4	$44.77	12.787%	$50.4947	$50.49	$50.50	$50.50
Purchase #5	$140.56	8.112%	$151.9622	$151.96	$151.95	$152.00
Purchase #6	$140.31	7.150%	$150.3422	$150.34	$150.35	$150.30
Purchase #7	$32.34	11.139%	$35.9424	$35.94	$35.95	$35.90
7 purchase totals =	$704.87		$763.8066	$763.80	$763.85	$763.70