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	$147.61	11.345%	$164.3564	$164.36	$164.35	$164.40
Purchase #2	$78.33	13.330%	$88.7714	$88.77	$88.75	$88.80
Purchase #3	$158.86	8.589%	$172.5045	$172.50	$172.50	$172.50
Purchase #4	$23.40	3.411%	$24.1982	$24.20	$24.20	$24.20
Purchase #5	$45.83	6.509%	$48.8131	$48.81	$48.80	$48.80
Purchase #6	$68.79	12.747%	$77.5587	$77.56	$77.55	$77.60
Purchase #7	$188.93	3.850%	$196.2038	$196.20	$196.20	$196.20
7 purchase totals =	$711.75		$772.4061	$772.40	$772.35	$772.50