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	$234.97	9.140%	$256.4463	$256.45	$256.45	$256.40
Purchase #2	$120.29	9.705%	$131.9641	$131.96	$131.95	$132.00
Purchase #3	$174.76	6.353%	$185.8625	$185.86	$185.85	$185.90
Purchase #4	$204.50	8.306%	$221.4858	$221.49	$221.50	$221.50
Purchase #5	$102.57	11.841%	$114.7153	$114.72	$114.70	$114.70
Purchase #6	$43.79	12.672%	$49.3391	$49.34	$49.35	$49.30
Purchase #7	$214.25	7.570%	$230.4687	$230.47	$230.45	$230.50
7 purchase totals =	$1,095.13		$1,190.2818	$1,190.29	$1,190.25	$1,190.30