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	$228.49	11.213%	$254.1106	$254.11	$254.10	$254.10
Purchase #2	$247.44	10.330%	$273.0006	$273.00	$273.00	$273.00
Purchase #3	$40.87	11.353%	$45.51	$45.51	$45.50	$45.50
Purchase #4	$98.75	9.247%	$107.8814	$107.88	$107.90	$107.90
Purchase #5	$102.49	8.769%	$111.4773	$111.48	$111.50	$111.50
Purchase #6	$158.51	6.538%	$168.8734	$168.87	$168.85	$168.90
Purchase #7	$117.70	10.294%	$129.816	$129.82	$129.80	$129.80
7 purchase totals =	$994.25		$1,090.6693	$1,090.67	$1,090.65	$1,090.70