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	$65.58	7.586%	$70.5549	$70.55	$70.55	$70.60
Purchase #2	$86.71	3.385%	$89.6451	$89.65	$89.65	$89.60
Purchase #3	$39.88	6.200%	$42.3526	$42.35	$42.35	$42.40
Purchase #4	$196.38	3.503%	$203.2592	$203.26	$203.25	$203.30
Purchase #5	$80.82	5.240%	$85.055	$85.06	$85.05	$85.10
Purchase #6	$238.47	3.576%	$246.9977	$247.00	$247.00	$247.00
Purchase #7	$187.29	11.513%	$208.8527	$208.85	$208.85	$208.90
7 purchase totals =	$895.13		$946.7172	$946.72	$946.70	$946.90