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	$109.28	4.152%	$113.8173	$113.82	$113.80	$113.80
Purchase #2	$50.89	7.762%	$54.8401	$54.84	$54.85	$54.80
Purchase #3	$55.75	3.629%	$57.7732	$57.77	$57.75	$57.80
Purchase #4	$140.64	12.710%	$158.5153	$158.52	$158.50	$158.50
Purchase #5	$90.60	5.338%	$95.4362	$95.44	$95.45	$95.40
Purchase #6	$225.95	7.680%	$243.303	$243.30	$243.30	$243.30
Purchase #7	$35.47	13.402%	$40.2237	$40.22	$40.20	$40.20
7 purchase totals =	$708.58		$763.9088	$763.91	$763.85	$763.80