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	$83.41	4.625%	$87.2677	$87.27	$87.25	$87.30
Purchase #2	$72.29	6.165%	$76.7467	$76.75	$76.75	$76.70
Purchase #3	$119.28	7.691%	$128.4538	$128.45	$128.45	$128.50
Purchase #4	$39.72	10.316%	$43.8175	$43.82	$43.80	$43.80
Purchase #5	$96.42	3.165%	$99.4717	$99.47	$99.45	$99.50
Purchase #6	$150.26	10.317%	$165.7623	$165.76	$165.75	$165.80
Purchase #7	$159.71	3.835%	$165.8349	$165.83	$165.85	$165.80
7 purchase totals =	$721.09		$767.3546	$767.35	$767.30	$767.40