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	$235.29	3.627%	$243.824	$243.82	$243.80	$243.80
Purchase #2	$227.26	12.747%	$256.2288	$256.23	$256.25	$256.20
Purchase #3	$215.73	10.440%	$238.2522	$238.25	$238.25	$238.30
Purchase #4	$66.42	9.159%	$72.5034	$72.50	$72.50	$72.50
Purchase #5	$125.34	11.780%	$140.1051	$140.11	$140.10	$140.10
Purchase #6	$99.82	4.103%	$103.9156	$103.92	$103.90	$103.90
Purchase #7	$124.50	11.796%	$139.186	$139.19	$139.20	$139.20
7 purchase totals =	$1,094.36		$1,194.0151	$1,194.02	$1,194.00	$1,194.00