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	$177.44	7.742%	$191.1774	$191.18	$191.20	$191.20
Purchase #2	$123.62	8.874%	$134.59	$134.59	$134.60	$134.60
Purchase #3	$197.43	7.643%	$212.5196	$212.52	$212.50	$212.50
Purchase #4	$183.61	3.415%	$189.8803	$189.88	$189.90	$189.90
Purchase #5	$140.61	4.501%	$146.9389	$146.94	$146.95	$146.90
Purchase #6	$141.38	4.161%	$147.2628	$147.26	$147.25	$147.30
Purchase #7	$232.64	10.236%	$256.453	$256.45	$256.45	$256.50
7 purchase totals =	$1,196.73		$1,278.8220	$1,278.82	$1,278.85	$1,278.90