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	$215.56	6.510%	$229.593	$229.59	$229.60	$229.60
Purchase #2	$235.56	10.450%	$260.176	$260.18	$260.20	$260.20
Purchase #3	$169.77	8.608%	$184.3838	$184.38	$184.40	$184.40
Purchase #4	$78.89	8.566%	$85.6477	$85.65	$85.65	$85.60
Purchase #5	$138.76	12.650%	$156.3131	$156.31	$156.30	$156.30
Purchase #6	$94.72	4.475%	$98.9587	$98.96	$98.95	$99.00
Purchase #7	$21.69	12.201%	$24.3364	$24.34	$24.35	$24.30
7 purchase totals =	$954.95		$1,039.4087	$1,039.41	$1,039.45	$1,039.40