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	$179.75	5.188%	$189.0754	$189.08	$189.10	$189.10
Purchase #2	$167.78	7.453%	$180.2846	$180.28	$180.30	$180.30
Purchase #3	$172.83	6.216%	$183.5731	$183.57	$183.55	$183.60
Purchase #4	$48.81	7.792%	$52.6133	$52.61	$52.60	$52.60
Purchase #5	$50.73	7.408%	$54.4881	$54.49	$54.50	$54.50
Purchase #6	$147.76	7.538%	$158.8981	$158.90	$158.90	$158.90
Purchase #7	$108.89	6.698%	$116.1835	$116.18	$116.20	$116.20
7 purchase totals =	$876.55		$935.1161	$935.11	$935.15	$935.20