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	$176.33	11.409%	$196.4475	$196.45	$196.45	$196.40
Purchase #2	$119.85	11.239%	$133.3199	$133.32	$133.30	$133.30
Purchase #3	$195.43	12.138%	$219.1513	$219.15	$219.15	$219.20
Purchase #4	$100.41	10.673%	$111.1268	$111.13	$111.15	$111.10
Purchase #5	$123.56	10.188%	$136.1483	$136.15	$136.15	$136.10
Purchase #6	$35.96	3.846%	$37.343	$37.34	$37.35	$37.30
Purchase #7	$136.99	5.706%	$144.8066	$144.81	$144.80	$144.80
7 purchase totals =	$888.53		$978.3434	$978.35	$978.35	$978.20