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	$30.59	3.120%	$31.5444	$31.54	$31.55	$31.50
Purchase #2	$69.70	8.378%	$75.5395	$75.54	$75.55	$75.50
Purchase #3	$191.80	4.504%	$200.4387	$200.44	$200.45	$200.40
Purchase #4	$250.63	3.431%	$259.2291	$259.23	$259.25	$259.20
Purchase #5	$236.47	8.299%	$256.0946	$256.09	$256.10	$256.10
Purchase #6	$88.51	13.610%	$100.5562	$100.56	$100.55	$100.60
Purchase #7	$169.81	6.818%	$181.3876	$181.39	$181.40	$181.40
7 purchase totals =	$1,037.51		$1,104.7901	$1,104.79	$1,104.85	$1,104.70