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	$208.74	13.318%	$236.54	$236.54	$236.55	$236.50
Purchase #2	$19.25	6.242%	$20.4516	$20.45	$20.45	$20.50
Purchase #3	$100.72	7.700%	$108.4754	$108.48	$108.50	$108.50
Purchase #4	$111.86	7.804%	$120.5896	$120.59	$120.60	$120.60
Purchase #5	$156.57	8.320%	$169.5966	$169.60	$169.60	$169.60
Purchase #6	$156.37	11.844%	$174.8905	$174.89	$174.90	$174.90
Purchase #7	$22.59	8.360%	$24.4785	$24.48	$24.50	$24.50
7 purchase totals =	$776.10		$855.0222	$855.03	$855.10	$855.10