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	$164.78	6.142%	$174.9008	$174.90	$174.90	$174.90
Purchase #2	$65.53	11.314%	$72.9441	$72.94	$72.95	$72.90
Purchase #3	$112.72	4.425%	$117.7079	$117.71	$117.70	$117.70
Purchase #4	$134.62	3.366%	$139.1513	$139.15	$139.15	$139.20
Purchase #5	$35.28	8.224%	$38.1814	$38.18	$38.20	$38.20
Purchase #6	$109.86	4.384%	$114.6763	$114.68	$114.70	$114.70
Purchase #7	$144.46	3.873%	$150.0549	$150.05	$150.05	$150.10
7 purchase totals =	$767.25		$807.6167	$807.61	$807.65	$807.70