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	$194.82	11.666%	$217.5477	$217.55	$217.55	$217.50
Purchase #2	$242.79	13.446%	$275.4355	$275.44	$275.45	$275.40
Purchase #3	$213.95	10.331%	$236.0532	$236.05	$236.05	$236.10
Purchase #4	$182.59	11.785%	$204.1082	$204.11	$204.10	$204.10
Purchase #5	$97.71	3.144%	$100.782	$100.78	$100.80	$100.80
Purchase #6	$124.40	13.546%	$141.2512	$141.25	$141.25	$141.30
Purchase #7	$103.31	9.713%	$113.3445	$113.34	$113.35	$113.30
7 purchase totals =	$1,159.57		$1,288.5223	$1,288.52	$1,288.55	$1,288.50