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	$65.93	9.564%	$72.2355	$72.24	$72.25	$72.20
Purchase #2	$247.68	5.231%	$260.6361	$260.64	$260.65	$260.60
Purchase #3	$135.38	9.524%	$148.2736	$148.27	$148.25	$148.30
Purchase #4	$180.64	5.318%	$190.2464	$190.25	$190.25	$190.20
Purchase #5	$72.87	5.184%	$76.6476	$76.65	$76.65	$76.60
Purchase #6	$155.89	13.459%	$176.8712	$176.87	$176.85	$176.90
Purchase #7	$157.80	7.532%	$169.6855	$169.69	$169.70	$169.70
7 purchase totals =	$1,016.19		$1,094.5959	$1,094.61	$1,094.60	$1,094.50