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	$183.29	8.318%	$198.5361	$198.54	$198.55	$198.50
Purchase #2	$33.72	6.419%	$35.8845	$35.88	$35.90	$35.90
Purchase #3	$118.75	10.477%	$131.1914	$131.19	$131.20	$131.20
Purchase #4	$250.76	9.870%	$275.51	$275.51	$275.50	$275.50
Purchase #5	$159.48	3.137%	$164.4829	$164.48	$164.50	$164.50
Purchase #6	$147.30	6.119%	$156.3133	$156.31	$156.30	$156.30
Purchase #7	$48.44	13.390%	$54.9261	$54.93	$54.95	$54.90
7 purchase totals =	$941.74		$1,016.8443	$1,016.84	$1,016.90	$1,016.80