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	$103.60	6.470%	$110.3029	$110.30	$110.30	$110.30
Purchase #2	$214.63	12.308%	$241.0467	$241.05	$241.05	$241.00
Purchase #3	$103.62	12.224%	$116.2865	$116.29	$116.30	$116.30
Purchase #4	$81.27	5.634%	$85.8488	$85.85	$85.85	$85.80
Purchase #5	$34.51	9.578%	$37.8154	$37.82	$37.80	$37.80
Purchase #6	$163.57	3.153%	$168.7274	$168.73	$168.75	$168.70
Purchase #7	$217.59	12.778%	$245.3937	$245.39	$245.40	$245.40
7 purchase totals =	$918.79		$1,005.4214	$1,005.43	$1,005.45	$1,005.30