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	$191.33	3.197%	$197.4468	$197.45	$197.45	$197.40
Purchase #2	$57.52	12.757%	$64.8578	$64.86	$64.85	$64.90
Purchase #3	$19.56	12.175%	$21.9414	$21.94	$21.95	$21.90
Purchase #4	$93.79	7.542%	$100.8636	$100.86	$100.85	$100.90
Purchase #5	$173.39	5.330%	$182.6317	$182.63	$182.65	$182.60
Purchase #6	$135.92	10.837%	$150.6497	$150.65	$150.65	$150.60
Purchase #7	$62.43	13.567%	$70.8999	$70.90	$70.90	$70.90
7 purchase totals =	$733.94		$789.2909	$789.29	$789.30	$789.20