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	$151.47	6.576%	$161.4307	$161.43	$161.45	$161.40
Purchase #2	$234.57	3.767%	$243.4063	$243.41	$243.40	$243.40
Purchase #3	$141.71	11.671%	$158.249	$158.25	$158.25	$158.20
Purchase #4	$245.87	7.193%	$263.5554	$263.56	$263.55	$263.60
Purchase #5	$115.27	11.407%	$128.4188	$128.42	$128.40	$128.40
Purchase #6	$165.52	3.688%	$171.6244	$171.62	$171.60	$171.60
Purchase #7	$119.81	7.531%	$128.8329	$128.83	$128.85	$128.80
7 purchase totals =	$1,174.22		$1,255.5175	$1,255.52	$1,255.50	$1,255.40