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	$118.54	8.365%	$128.4559	$128.46	$128.45	$128.50
Purchase #2	$164.48	3.180%	$169.7105	$169.71	$169.70	$169.70
Purchase #3	$70.87	3.132%	$73.0896	$73.09	$73.10	$73.10
Purchase #4	$81.71	4.496%	$85.3837	$85.38	$85.40	$85.40
Purchase #5	$81.86	11.675%	$91.4172	$91.42	$91.40	$91.40
Purchase #6	$42.73	5.428%	$45.0494	$45.05	$45.05	$45.00
Purchase #7	$13.75	5.755%	$14.5413	$14.54	$14.55	$14.50
7 purchase totals =	$573.94		$607.6476	$607.65	$607.65	$607.60