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	$110.78	11.505%	$123.5252	$123.53	$123.55	$123.50
Purchase #2	$131.98	6.473%	$140.5231	$140.52	$140.50	$140.50
Purchase #3	$152.30	12.229%	$170.9248	$170.92	$170.90	$170.90
Purchase #4	$166.69	3.716%	$172.8842	$172.88	$172.90	$172.90
Purchase #5	$59.30	8.821%	$64.5309	$64.53	$64.55	$64.50
Purchase #6	$63.72	13.393%	$72.254	$72.25	$72.25	$72.30
Purchase #7	$137.30	10.373%	$151.5421	$151.54	$151.55	$151.50
7 purchase totals =	$822.07		$896.1843	$896.17	$896.20	$896.10