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	$60.56	7.840%	$65.3079	$65.31	$65.30	$65.30
Purchase #2	$96.75	12.207%	$108.5603	$108.56	$108.55	$108.60
Purchase #3	$174.51	5.405%	$183.9423	$183.94	$183.95	$183.90
Purchase #4	$122.95	6.192%	$130.5631	$130.56	$130.55	$130.60
Purchase #5	$228.90	11.830%	$255.9789	$255.98	$256.00	$256.00
Purchase #6	$33.93	4.474%	$35.448	$35.45	$35.45	$35.40
Purchase #7	$216.86	9.137%	$236.6745	$236.67	$236.65	$236.70
7 purchase totals =	$934.46		$1,016.4750	$1,016.47	$1,016.45	$1,016.50