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	$33.38	12.177%	$37.4447	$37.44	$37.45	$37.40
Purchase #2	$74.44	5.800%	$78.7575	$78.76	$78.75	$78.80
Purchase #3	$55.64	12.825%	$62.7758	$62.78	$62.80	$62.80
Purchase #4	$113.65	4.619%	$118.8995	$118.90	$118.90	$118.90
Purchase #5	$201.97	9.162%	$220.4745	$220.47	$220.45	$220.50
Purchase #6	$79.40	4.594%	$83.0476	$83.05	$83.05	$83.00
Purchase #7	$205.40	4.728%	$215.1113	$215.11	$215.10	$215.10
7 purchase totals =	$763.88		$816.5109	$816.51	$816.50	$816.50