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	$205.30	12.838%	$231.6564	$231.66	$231.65	$231.70
Purchase #2	$42.77	10.282%	$47.1676	$47.17	$47.15	$47.20
Purchase #3	$188.48	11.596%	$210.3361	$210.34	$210.35	$210.30
Purchase #4	$99.58	10.363%	$109.8995	$109.90	$109.90	$109.90
Purchase #5	$186.56	13.414%	$211.5852	$211.59	$211.60	$211.60
Purchase #6	$194.61	12.853%	$219.6232	$219.62	$219.60	$219.60
Purchase #7	$29.76	8.257%	$32.2173	$32.22	$32.20	$32.20
7 purchase totals =	$947.06		$1,062.4853	$1,062.50	$1,062.45	$1,062.50