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	$233.71	4.802%	$244.9328	$244.93	$244.95	$244.90
Purchase #2	$191.92	9.789%	$210.707	$210.71	$210.70	$210.70
Purchase #3	$63.57	6.763%	$67.8692	$67.87	$67.85	$67.90
Purchase #4	$170.42	8.807%	$185.4289	$185.43	$185.45	$185.40
Purchase #5	$72.49	7.126%	$77.6556	$77.66	$77.65	$77.70
Purchase #6	$10.78	11.582%	$12.0285	$12.03	$12.05	$12.00
Purchase #7	$56.95	4.719%	$59.6375	$59.64	$59.65	$59.60
7 purchase totals =	$799.84		$858.2595	$858.27	$858.30	$858.20