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	$159.68	8.186%	$172.7514	$172.75	$172.75	$172.80
Purchase #2	$29.69	10.815%	$32.901	$32.90	$32.90	$32.90
Purchase #3	$52.72	12.670%	$59.3996	$59.40	$59.40	$59.40
Purchase #4	$84.88	7.874%	$91.5635	$91.56	$91.55	$91.60
Purchase #5	$71.45	7.666%	$76.9274	$76.93	$76.95	$76.90
Purchase #6	$209.37	10.776%	$231.9317	$231.93	$231.95	$231.90
Purchase #7	$70.98	3.433%	$73.4167	$73.42	$73.40	$73.40
7 purchase totals =	$678.77		$738.8913	$738.89	$738.90	$738.90