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	$241.73	3.429%	$250.0189	$250.02	$250.00	$250.00
Purchase #2	$6.54	3.613%	$6.7763	$6.78	$6.80	$6.80
Purchase #3	$126.68	10.381%	$139.8307	$139.83	$139.85	$139.80
Purchase #4	$228.56	6.706%	$243.8872	$243.89	$243.90	$243.90
Purchase #5	$247.53	11.243%	$275.3598	$275.36	$275.35	$275.40
Purchase #6	$167.82	6.842%	$179.3022	$179.30	$179.30	$179.30
Purchase #7	$52.86	8.647%	$57.4308	$57.43	$57.45	$57.40
7 purchase totals =	$1,071.72		$1,152.6059	$1,152.61	$1,152.65	$1,152.60