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	$40.51	11.282%	$45.0803	$45.08	$45.10	$45.10
Purchase #2	$130.29	10.338%	$143.7594	$143.76	$143.75	$143.80
Purchase #3	$97.93	13.477%	$111.128	$111.13	$111.15	$111.10
Purchase #4	$102.63	9.450%	$112.3285	$112.33	$112.35	$112.30
Purchase #5	$235.34	4.734%	$246.481	$246.48	$246.50	$246.50
Purchase #6	$75.29	6.708%	$80.3405	$80.34	$80.35	$80.30
Purchase #7	$140.40	4.375%	$146.5425	$146.54	$146.55	$146.50
7 purchase totals =	$822.39		$885.6602	$885.66	$885.75	$885.60