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	$32.86	7.146%	$35.2082	$35.21	$35.20	$35.20
Purchase #2	$82.37	8.269%	$89.1812	$89.18	$89.20	$89.20
Purchase #3	$31.63	4.444%	$33.0356	$33.04	$33.05	$33.00
Purchase #4	$82.72	5.556%	$87.3159	$87.32	$87.30	$87.30
Purchase #5	$34.57	3.725%	$35.8577	$35.86	$35.85	$35.90
Purchase #6	$179.82	11.137%	$199.8466	$199.85	$199.85	$199.80
Purchase #7	$192.51	10.464%	$212.6542	$212.65	$212.65	$212.70
7 purchase totals =	$636.48		$693.0994	$693.11	$693.10	$693.10