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	$126.36	4.250%	$131.7303	$131.73	$131.75	$131.70
Purchase #2	$52.57	7.770%	$56.6547	$56.65	$56.65	$56.70
Purchase #3	$242.37	7.161%	$259.7261	$259.73	$259.75	$259.70
Purchase #4	$223.25	9.201%	$243.7912	$243.79	$243.80	$243.80
Purchase #5	$26.87	12.617%	$30.2602	$30.26	$30.25	$30.30
Purchase #6	$144.86	4.193%	$150.934	$150.93	$150.95	$150.90
Purchase #7	$126.51	13.214%	$143.227	$143.23	$143.25	$143.20
7 purchase totals =	$942.79		$1,016.3235	$1,016.32	$1,016.40	$1,016.30