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	$132.68	3.854%	$137.7935	$137.79	$137.80	$137.80
Purchase #2	$89.83	5.246%	$94.5425	$94.54	$94.55	$94.50
Purchase #3	$57.29	5.212%	$60.276	$60.28	$60.30	$60.30
Purchase #4	$196.77	13.510%	$223.3536	$223.35	$223.35	$223.40
Purchase #5	$133.33	4.221%	$138.9579	$138.96	$138.95	$139.00
Purchase #6	$194.31	11.425%	$216.5099	$216.51	$216.50	$216.50
Purchase #7	$83.79	10.839%	$92.872	$92.87	$92.85	$92.90
7 purchase totals =	$888.00		$964.3054	$964.30	$964.30	$964.40