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	$75.53	9.427%	$82.6502	$82.65	$82.65	$82.70
Purchase #2	$197.85	10.546%	$218.7153	$218.72	$218.70	$218.70
Purchase #3	$112.61	9.263%	$123.0411	$123.04	$123.05	$123.00
Purchase #4	$52.87	8.282%	$57.2487	$57.25	$57.25	$57.20
Purchase #5	$220.96	3.510%	$228.7157	$228.72	$228.70	$228.70
Purchase #6	$40.85	13.288%	$46.2781	$46.28	$46.30	$46.30
Purchase #7	$173.61	6.136%	$184.2627	$184.26	$184.25	$184.30
7 purchase totals =	$874.28		$940.9118	$940.92	$940.90	$940.90