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	$143.28	9.742%	$157.2383	$157.24	$157.25	$157.20
Purchase #2	$243.57	4.179%	$253.7488	$253.75	$253.75	$253.70
Purchase #3	$164.82	12.604%	$185.5939	$185.59	$185.60	$185.60
Purchase #4	$116.96	5.260%	$123.1121	$123.11	$123.10	$123.10
Purchase #5	$95.52	10.619%	$105.6633	$105.66	$105.65	$105.70
Purchase #6	$119.57	5.515%	$126.1643	$126.16	$126.15	$126.20
Purchase #7	$168.97	4.248%	$176.1478	$176.15	$176.15	$176.10
7 purchase totals =	$1,052.69		$1,127.6685	$1,127.66	$1,127.65	$1,127.60