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	$152.95	3.695%	$158.6015	$158.60	$158.60	$158.60
Purchase #2	$129.71	9.652%	$142.2296	$142.23	$142.25	$142.20
Purchase #3	$37.47	8.282%	$40.5733	$40.57	$40.55	$40.60
Purchase #4	$239.89	5.785%	$253.7676	$253.77	$253.75	$253.80
Purchase #5	$205.55	11.238%	$228.6497	$228.65	$228.65	$228.60
Purchase #6	$188.43	10.623%	$208.4469	$208.45	$208.45	$208.40
Purchase #7	$114.39	5.676%	$120.8828	$120.88	$120.90	$120.90
7 purchase totals =	$1,068.39		$1,153.1514	$1,153.15	$1,153.15	$1,153.10