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	$218.66	9.828%	$240.1499	$240.15	$240.15	$240.10
Purchase #2	$36.66	4.870%	$38.4453	$38.45	$38.45	$38.40
Purchase #3	$31.36	3.679%	$32.5137	$32.51	$32.50	$32.50
Purchase #4	$101.40	13.166%	$114.7503	$114.75	$114.75	$114.80
Purchase #5	$105.82	13.316%	$119.911	$119.91	$119.90	$119.90
Purchase #6	$98.27	13.754%	$111.7861	$111.79	$111.80	$111.80
Purchase #7	$39.96	12.620%	$45.003	$45.00	$45.00	$45.00
7 purchase totals =	$632.13		$702.5593	$702.56	$702.55	$702.50