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	$220.41	11.766%	$246.3434	$246.34	$246.35	$246.30
Purchase #2	$234.70	7.177%	$251.5444	$251.54	$251.55	$251.50
Purchase #3	$33.97	9.596%	$37.2298	$37.23	$37.25	$37.20
Purchase #4	$201.76	3.542%	$208.9063	$208.91	$208.90	$208.90
Purchase #5	$115.43	10.768%	$127.8595	$127.86	$127.85	$127.90
Purchase #6	$142.54	7.804%	$153.6638	$153.66	$153.65	$153.70
Purchase #7	$38.86	8.782%	$42.2727	$42.27	$42.25	$42.30
7 purchase totals =	$987.67		$1,067.8199	$1,067.81	$1,067.80	$1,067.80