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	$233.52	7.470%	$250.9639	$250.96	$250.95	$251.00
Purchase #2	$131.93	7.409%	$141.7047	$141.70	$141.70	$141.70
Purchase #3	$146.64	12.874%	$165.5184	$165.52	$165.50	$165.50
Purchase #4	$43.66	13.466%	$49.5393	$49.54	$49.55	$49.50
Purchase #5	$70.72	4.447%	$73.8649	$73.86	$73.85	$73.90
Purchase #6	$69.92	3.366%	$72.2735	$72.27	$72.25	$72.30
Purchase #7	$189.84	13.833%	$216.1006	$216.10	$216.10	$216.10
7 purchase totals =	$886.23		$969.9653	$969.95	$969.90	$970.00