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	$215.38	4.492%	$225.0549	$225.05	$225.05	$225.10
Purchase #2	$77.86	6.660%	$83.0455	$83.05	$83.05	$83.00
Purchase #3	$220.66	13.754%	$251.0096	$251.01	$251.00	$251.00
Purchase #4	$116.91	5.760%	$123.644	$123.64	$123.65	$123.60
Purchase #5	$38.85	10.457%	$42.9125	$42.91	$42.90	$42.90
Purchase #6	$39.94	3.593%	$41.375	$41.38	$41.40	$41.40
Purchase #7	$22.33	13.225%	$25.2831	$25.28	$25.30	$25.30
7 purchase totals =	$731.93		$792.3246	$792.32	$792.35	$792.30