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	$205.56	11.440%	$229.0761	$229.08	$229.10	$229.10
Purchase #2	$68.72	3.600%	$71.1939	$71.19	$71.20	$71.20
Purchase #3	$60.96	7.713%	$65.6618	$65.66	$65.65	$65.70
Purchase #4	$158.38	13.117%	$179.1547	$179.15	$179.15	$179.20
Purchase #5	$17.84	5.192%	$18.7663	$18.77	$18.75	$18.80
Purchase #6	$236.78	8.360%	$256.5748	$256.57	$256.55	$256.60
Purchase #7	$164.46	11.566%	$183.4814	$183.48	$183.50	$183.50
7 purchase totals =	$912.70		$1,003.9090	$1,003.90	$1,003.90	$1,004.10