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	$66.36	8.806%	$72.2037	$72.20	$72.20	$72.20
Purchase #2	$208.31	11.798%	$232.8864	$232.89	$232.90	$232.90
Purchase #3	$180.37	4.821%	$189.0656	$189.07	$189.05	$189.10
Purchase #4	$136.74	9.685%	$149.9833	$149.98	$150.00	$150.00
Purchase #5	$223.97	13.743%	$254.7502	$254.75	$254.75	$254.80
Purchase #6	$150.90	9.339%	$164.9926	$164.99	$165.00	$165.00
Purchase #7	$56.31	5.627%	$59.4786	$59.48	$59.50	$59.50
7 purchase totals =	$1,022.96		$1,123.3604	$1,123.36	$1,123.40	$1,123.50