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	$8.29	5.522%	$8.7478	$8.75	$8.75	$8.70
Purchase #2	$197.71	5.692%	$208.9637	$208.96	$208.95	$209.00
Purchase #3	$82.57	9.546%	$90.4521	$90.45	$90.45	$90.50
Purchase #4	$225.47	13.839%	$256.6728	$256.67	$256.65	$256.70
Purchase #5	$81.32	5.530%	$85.817	$85.82	$85.80	$85.80
Purchase #6	$172.37	9.368%	$188.5176	$188.52	$188.50	$188.50
Purchase #7	$146.53	6.338%	$155.8171	$155.82	$155.80	$155.80
7 purchase totals =	$914.26		$994.9881	$994.99	$994.90	$995.00