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	$83.58	3.371%	$86.3975	$86.40	$86.40	$86.40
Purchase #2	$42.60	11.844%	$47.6455	$47.65	$47.65	$47.60
Purchase #3	$40.53	13.759%	$46.1065	$46.11	$46.10	$46.10
Purchase #4	$58.39	7.703%	$62.8878	$62.89	$62.90	$62.90
Purchase #5	$146.56	7.828%	$158.0327	$158.03	$158.05	$158.00
Purchase #6	$72.74	12.569%	$81.8827	$81.88	$81.90	$81.90
Purchase #7	$161.95	5.808%	$171.3561	$171.36	$171.35	$171.40
7 purchase totals =	$606.35		$654.3088	$654.32	$654.35	$654.30