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	$85.66	5.464%	$90.3405	$90.34	$90.35	$90.30
Purchase #2	$196.35	3.576%	$203.3715	$203.37	$203.35	$203.40
Purchase #3	$44.95	12.581%	$50.6052	$50.61	$50.60	$50.60
Purchase #4	$149.43	11.822%	$167.0956	$167.10	$167.10	$167.10
Purchase #5	$210.62	12.146%	$236.2019	$236.20	$236.20	$236.20
Purchase #6	$108.42	4.456%	$113.2512	$113.25	$113.25	$113.30
Purchase #7	$135.31	12.291%	$151.941	$151.94	$151.95	$151.90
7 purchase totals =	$930.74		$1,012.8069	$1,012.81	$1,012.80	$1,012.80