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	$140.35	12.538%	$157.9471	$157.95	$157.95	$157.90
Purchase #2	$201.51	5.250%	$212.0893	$212.09	$212.10	$212.10
Purchase #3	$41.53	9.334%	$45.4064	$45.41	$45.40	$45.40
Purchase #4	$188.95	11.831%	$211.3047	$211.30	$211.30	$211.30
Purchase #5	$212.89	9.248%	$232.5781	$232.58	$232.60	$232.60
Purchase #6	$82.46	3.714%	$85.5226	$85.52	$85.50	$85.50
Purchase #7	$52.36	4.443%	$54.6864	$54.69	$54.70	$54.70
7 purchase totals =	$920.05		$999.5346	$999.54	$999.55	$999.50