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	$95.42	3.183%	$98.4572	$98.46	$98.45	$98.50
Purchase #2	$150.61	12.542%	$169.4995	$169.50	$169.50	$169.50
Purchase #3	$50.72	5.756%	$53.6394	$53.64	$53.65	$53.60
Purchase #4	$167.78	11.870%	$187.6955	$187.70	$187.70	$187.70
Purchase #5	$107.94	8.787%	$117.4247	$117.42	$117.40	$117.40
Purchase #6	$165.53	5.655%	$174.8907	$174.89	$174.90	$174.90
Purchase #7	$62.52	13.629%	$71.0409	$71.04	$71.05	$71.00
7 purchase totals =	$800.52		$872.6479	$872.65	$872.65	$872.60