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	$213.71	5.390%	$225.229	$225.23	$225.25	$225.20
Purchase #2	$90.91	13.773%	$103.431	$103.43	$103.45	$103.40
Purchase #3	$80.94	5.124%	$85.0874	$85.09	$85.10	$85.10
Purchase #4	$11.41	12.298%	$12.8132	$12.81	$12.80	$12.80
Purchase #5	$216.79	7.676%	$233.4308	$233.43	$233.45	$233.40
Purchase #6	$233.71	9.792%	$256.5949	$256.59	$256.60	$256.60
Purchase #7	$190.30	11.321%	$211.8439	$211.84	$211.85	$211.80
7 purchase totals =	$1,037.77		$1,128.4302	$1,128.42	$1,128.50	$1,128.30