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	$179.84	11.709%	$200.8975	$200.90	$200.90	$200.90
Purchase #2	$78.52	9.380%	$85.8852	$85.89	$85.90	$85.90
Purchase #3	$56.67	5.823%	$59.9699	$59.97	$59.95	$60.00
Purchase #4	$217.41	6.218%	$230.9286	$230.93	$230.95	$230.90
Purchase #5	$139.70	5.574%	$147.4869	$147.49	$147.50	$147.50
Purchase #6	$29.70	11.349%	$33.0707	$33.07	$33.05	$33.10
Purchase #7	$155.25	12.510%	$174.6718	$174.67	$174.65	$174.70
7 purchase totals =	$857.09		$932.9106	$932.92	$932.90	$933.00