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	$148.57	5.592%	$156.878	$156.88	$156.90	$156.90
Purchase #2	$68.99	4.380%	$72.0118	$72.01	$72.00	$72.00
Purchase #3	$61.82	5.420%	$65.1706	$65.17	$65.15	$65.20
Purchase #4	$182.66	7.351%	$196.0873	$196.09	$196.10	$196.10
Purchase #5	$51.63	5.595%	$54.5187	$54.52	$54.50	$54.50
Purchase #6	$238.76	10.220%	$263.1613	$263.16	$263.15	$263.20
Purchase #7	$175.56	5.778%	$185.7039	$185.70	$185.70	$185.70
7 purchase totals =	$927.99		$993.5316	$993.53	$993.50	$993.60