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	$221.59	3.148%	$228.5657	$228.57	$228.55	$228.60
Purchase #2	$190.64	8.366%	$206.5889	$206.59	$206.60	$206.60
Purchase #3	$120.50	9.367%	$131.7872	$131.79	$131.80	$131.80
Purchase #4	$41.36	12.503%	$46.5312	$46.53	$46.55	$46.50
Purchase #5	$180.89	9.163%	$197.465	$197.47	$197.45	$197.50
Purchase #6	$48.28	12.783%	$54.4516	$54.45	$54.45	$54.50
Purchase #7	$18.56	10.814%	$20.5671	$20.57	$20.55	$20.60
7 purchase totals =	$821.82		$885.9567	$885.97	$885.95	$886.10