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	$155.56	4.144%	$162.0064	$162.01	$162.00	$162.00
Purchase #2	$94.44	6.195%	$100.2906	$100.29	$100.30	$100.30
Purchase #3	$71.42	12.822%	$80.5775	$80.58	$80.60	$80.60
Purchase #4	$247.68	4.778%	$259.5142	$259.51	$259.50	$259.50
Purchase #5	$157.50	6.596%	$167.8887	$167.89	$167.90	$167.90
Purchase #6	$183.72	3.252%	$189.6946	$189.69	$189.70	$189.70
Purchase #7	$195.50	10.620%	$216.2621	$216.26	$216.25	$216.30
7 purchase totals =	$1,105.82		$1,176.2341	$1,176.23	$1,176.25	$1,176.30