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	$133.98	13.168%	$151.6225	$151.62	$151.60	$151.60
Purchase #2	$64.51	12.531%	$72.5937	$72.59	$72.60	$72.60
Purchase #3	$139.70	3.567%	$144.6831	$144.68	$144.70	$144.70
Purchase #4	$237.27	8.850%	$258.2684	$258.27	$258.25	$258.30
Purchase #5	$159.95	12.166%	$179.4095	$179.41	$179.40	$179.40
Purchase #6	$101.31	12.465%	$113.9383	$113.94	$113.95	$113.90
Purchase #7	$47.98	7.813%	$51.7287	$51.73	$51.75	$51.70
7 purchase totals =	$884.70		$972.2442	$972.24	$972.25	$972.20