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	$74.48	3.317%	$76.9505	$76.95	$76.95	$77.00
Purchase #2	$97.87	11.735%	$109.355	$109.36	$109.35	$109.40
Purchase #3	$117.82	7.373%	$126.5069	$126.51	$126.50	$126.50
Purchase #4	$214.40	3.570%	$222.0541	$222.05	$222.05	$222.10
Purchase #5	$90.57	9.589%	$99.2548	$99.25	$99.25	$99.30
Purchase #6	$59.64	12.649%	$67.1839	$67.18	$67.20	$67.20
Purchase #7	$130.93	8.325%	$141.8299	$141.83	$141.85	$141.80
7 purchase totals =	$785.71		$843.1351	$843.13	$843.15	$843.30