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	$109.87	4.556%	$114.8757	$114.88	$114.90	$114.90
Purchase #2	$54.82	8.628%	$59.5499	$59.55	$59.55	$59.50
Purchase #3	$238.65	6.590%	$254.377	$254.38	$254.40	$254.40
Purchase #4	$157.78	13.107%	$178.4602	$178.46	$178.45	$178.50
Purchase #5	$131.32	11.825%	$146.8486	$146.85	$146.85	$146.80
Purchase #6	$105.45	11.828%	$117.9226	$117.92	$117.90	$117.90
Purchase #7	$148.63	6.599%	$158.4381	$158.44	$158.45	$158.40
7 purchase totals =	$946.52		$1,030.4721	$1,030.48	$1,030.50	$1,030.40