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	$197.48	8.624%	$214.5107	$214.51	$214.50	$214.50
Purchase #2	$135.99	11.349%	$151.4235	$151.42	$151.40	$151.40
Purchase #3	$32.70	8.501%	$35.4798	$35.48	$35.50	$35.50
Purchase #4	$55.67	9.769%	$61.1084	$61.11	$61.10	$61.10
Purchase #5	$151.81	11.218%	$168.84	$168.84	$168.85	$168.80
Purchase #6	$172.96	13.568%	$196.4272	$196.43	$196.45	$196.40
Purchase #7	$244.36	8.544%	$265.2381	$265.24	$265.25	$265.20
7 purchase totals =	$990.97		$1,093.0277	$1,093.03	$1,093.05	$1,092.90