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	$191.33	13.444%	$217.0524	$217.05	$217.05	$217.10
Purchase #2	$216.29	6.702%	$230.7858	$230.79	$230.80	$230.80
Purchase #3	$82.73	8.731%	$89.9532	$89.95	$89.95	$90.00
Purchase #4	$97.39	3.204%	$100.5104	$100.51	$100.50	$100.50
Purchase #5	$109.97	4.288%	$114.6855	$114.69	$114.70	$114.70
Purchase #6	$31.91	9.557%	$34.9596	$34.96	$34.95	$35.00
Purchase #7	$150.89	13.239%	$170.8663	$170.87	$170.85	$170.90
7 purchase totals =	$880.51		$958.8132	$958.82	$958.80	$959.00