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	$38.83	10.608%	$42.9491	$42.95	$42.95	$42.90
Purchase #2	$198.90	13.471%	$225.6938	$225.69	$225.70	$225.70
Purchase #3	$37.82	6.827%	$40.402	$40.40	$40.40	$40.40
Purchase #4	$101.66	10.516%	$112.3506	$112.35	$112.35	$112.40
Purchase #5	$16.53	3.766%	$17.1525	$17.15	$17.15	$17.20
Purchase #6	$46.48	9.496%	$50.8937	$50.89	$50.90	$50.90
Purchase #7	$147.59	12.279%	$165.7126	$165.71	$165.70	$165.70
7 purchase totals =	$587.81		$655.1543	$655.14	$655.15	$655.20