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	$151.59	5.159%	$159.4105	$159.41	$159.40	$159.40
Purchase #2	$63.64	13.758%	$72.3956	$72.40	$72.40	$72.40
Purchase #3	$44.73	4.776%	$46.8663	$46.87	$46.85	$46.90
Purchase #4	$152.61	6.527%	$162.5709	$162.57	$162.55	$162.60
Purchase #5	$99.92	13.428%	$113.3373	$113.34	$113.35	$113.30
Purchase #6	$200.43	6.541%	$213.5401	$213.54	$213.55	$213.50
Purchase #7	$192.89	3.708%	$200.0424	$200.04	$200.05	$200.00
7 purchase totals =	$905.81		$968.1631	$968.17	$968.15	$968.10