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	$104.41	7.743%	$112.4945	$112.49	$112.50	$112.50
Purchase #2	$57.33	6.718%	$61.1814	$61.18	$61.20	$61.20
Purchase #3	$150.96	8.300%	$163.4897	$163.49	$163.50	$163.50
Purchase #4	$128.84	12.561%	$145.0236	$145.02	$145.00	$145.00
Purchase #5	$90.78	11.143%	$100.8956	$100.90	$100.90	$100.90
Purchase #6	$39.75	6.116%	$42.1811	$42.18	$42.20	$42.20
Purchase #7	$161.87	3.189%	$167.032	$167.03	$167.05	$167.00
7 purchase totals =	$733.94		$792.2979	$792.29	$792.35	$792.30