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	$87.89	4.563%	$91.9004	$91.90	$91.90	$91.90
Purchase #2	$181.37	13.243%	$205.3888	$205.39	$205.40	$205.40
Purchase #3	$148.62	12.300%	$166.9003	$166.90	$166.90	$166.90
Purchase #4	$229.68	11.841%	$256.8764	$256.88	$256.90	$256.90
Purchase #5	$170.97	12.230%	$191.8796	$191.88	$191.90	$191.90
Purchase #6	$143.79	11.105%	$159.7579	$159.76	$159.75	$159.80
Purchase #7	$19.53	11.254%	$21.7279	$21.73	$21.75	$21.70
7 purchase totals =	$981.85		$1,094.4313	$1,094.44	$1,094.50	$1,094.50