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	$93.85	5.650%	$99.1525	$99.15	$99.15	$99.20
Purchase #2	$61.25	7.544%	$65.8707	$65.87	$65.85	$65.90
Purchase #3	$89.36	12.127%	$100.1967	$100.20	$100.20	$100.20
Purchase #4	$113.86	10.287%	$125.5728	$125.57	$125.55	$125.60
Purchase #5	$197.59	7.246%	$211.9074	$211.91	$211.90	$211.90
Purchase #6	$137.54	6.404%	$146.3481	$146.35	$146.35	$146.30
Purchase #7	$177.68	8.259%	$192.3546	$192.35	$192.35	$192.40
7 purchase totals =	$871.13		$941.4028	$941.40	$941.35	$941.50