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	$241.43	6.808%	$257.8666	$257.87	$257.85	$257.90
Purchase #2	$243.37	9.393%	$266.2297	$266.23	$266.25	$266.20
Purchase #3	$39.39	7.848%	$42.4813	$42.48	$42.50	$42.50
Purchase #4	$86.85	7.601%	$93.4515	$93.45	$93.45	$93.50
Purchase #5	$139.71	5.628%	$147.5729	$147.57	$147.55	$147.60
Purchase #6	$86.77	13.845%	$98.7833	$98.78	$98.80	$98.80
Purchase #7	$170.72	9.820%	$187.4847	$187.48	$187.50	$187.50
7 purchase totals =	$1,008.24		$1,093.8700	$1,093.86	$1,093.90	$1,094.00