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	$124.83	4.634%	$130.6146	$130.61	$130.60	$130.60
Purchase #2	$15.94	11.575%	$17.7851	$17.79	$17.80	$17.80
Purchase #3	$244.73	8.614%	$265.811	$265.81	$265.80	$265.80
Purchase #4	$78.92	13.848%	$89.8488	$89.85	$89.85	$89.80
Purchase #5	$105.84	13.698%	$120.338	$120.34	$120.35	$120.30
Purchase #6	$189.61	9.448%	$207.5244	$207.52	$207.50	$207.50
Purchase #7	$79.96	6.790%	$85.3893	$85.39	$85.40	$85.40
7 purchase totals =	$839.83		$917.3112	$917.31	$917.30	$917.20