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	$50.85	3.741%	$52.7523	$52.75	$52.75	$52.80
Purchase #2	$77.64	3.505%	$80.3613	$80.36	$80.35	$80.40
Purchase #3	$154.45	11.513%	$172.2318	$172.23	$172.25	$172.20
Purchase #4	$127.38	7.864%	$137.3972	$137.40	$137.40	$137.40
Purchase #5	$207.40	10.505%	$229.1874	$229.19	$229.20	$229.20
Purchase #6	$234.52	11.317%	$261.0606	$261.06	$261.05	$261.10
Purchase #7	$161.67	6.503%	$172.1834	$172.18	$172.20	$172.20
7 purchase totals =	$1,013.91		$1,105.1740	$1,105.17	$1,105.20	$1,105.30