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	$11.54	3.473%	$11.9408	$11.94	$11.95	$11.90
Purchase #2	$65.71	7.507%	$70.6428	$70.64	$70.65	$70.60
Purchase #3	$113.97	8.174%	$123.2859	$123.29	$123.30	$123.30
Purchase #4	$150.44	11.358%	$167.527	$167.53	$167.55	$167.50
Purchase #5	$151.88	10.118%	$167.2472	$167.25	$167.25	$167.20
Purchase #6	$210.63	5.469%	$222.1494	$222.15	$222.15	$222.10
Purchase #7	$178.28	6.129%	$189.2068	$189.21	$189.20	$189.20
7 purchase totals =	$882.45		$951.9999	$952.01	$952.05	$951.80