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	$55.67	6.463%	$59.268	$59.27	$59.25	$59.30
Purchase #2	$79.56	11.334%	$88.5773	$88.58	$88.60	$88.60
Purchase #3	$172.86	4.123%	$179.987	$179.99	$180.00	$180.00
Purchase #4	$28.62	3.157%	$29.5235	$29.52	$29.50	$29.50
Purchase #5	$195.67	5.524%	$206.4788	$206.48	$206.50	$206.50
Purchase #6	$45.41	4.586%	$47.4925	$47.49	$47.50	$47.50
Purchase #7	$83.86	7.511%	$90.1587	$90.16	$90.15	$90.20
7 purchase totals =	$661.65		$701.4858	$701.49	$701.50	$701.60