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	$65.73	8.720%	$71.4617	$71.46	$71.45	$71.50
Purchase #2	$193.29	6.177%	$205.2295	$205.23	$205.25	$205.20
Purchase #3	$32.53	13.637%	$36.9661	$36.97	$36.95	$37.00
Purchase #4	$201.74	6.827%	$215.5128	$215.51	$215.50	$215.50
Purchase #5	$71.38	3.582%	$73.9368	$73.94	$73.95	$73.90
Purchase #6	$226.45	13.514%	$257.0525	$257.05	$257.05	$257.10
Purchase #7	$140.30	11.281%	$156.1272	$156.13	$156.15	$156.10
7 purchase totals =	$931.42		$1,016.2866	$1,016.29	$1,016.30	$1,016.30