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	$232.34	13.734%	$264.2496	$264.25	$264.25	$264.20
Purchase #2	$166.58	3.463%	$172.3487	$172.35	$172.35	$172.30
Purchase #3	$11.56	3.595%	$11.9756	$11.98	$12.00	$12.00
Purchase #4	$102.53	11.472%	$114.2922	$114.29	$114.30	$114.30
Purchase #5	$62.72	4.582%	$65.5938	$65.59	$65.60	$65.60
Purchase #6	$65.99	9.145%	$72.0248	$72.02	$72.00	$72.00
Purchase #7	$148.93	13.799%	$169.4809	$169.48	$169.50	$169.50
7 purchase totals =	$790.65		$869.9656	$869.96	$870.00	$869.90