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	$95.90	3.630%	$99.3812	$99.38	$99.40	$99.40
Purchase #2	$68.45	12.758%	$77.1829	$77.18	$77.20	$77.20
Purchase #3	$243.58	6.627%	$259.722	$259.72	$259.70	$259.70
Purchase #4	$199.83	11.792%	$223.394	$223.39	$223.40	$223.40
Purchase #5	$205.48	10.441%	$226.9342	$226.93	$226.95	$226.90
Purchase #6	$227.80	7.647%	$245.2199	$245.22	$245.20	$245.20
Purchase #7	$76.42	11.678%	$85.3443	$85.34	$85.35	$85.30
7 purchase totals =	$1,117.46		$1,217.1785	$1,217.16	$1,217.20	$1,217.10