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	$217.88	8.555%	$236.5196	$236.52	$236.50	$236.50
Purchase #2	$188.84	12.168%	$211.8181	$211.82	$211.80	$211.80
Purchase #3	$56.61	11.441%	$63.0868	$63.09	$63.10	$63.10
Purchase #4	$167.25	3.506%	$173.1138	$173.11	$173.10	$173.10
Purchase #5	$150.29	7.699%	$161.8608	$161.86	$161.85	$161.90
Purchase #6	$39.75	13.253%	$45.0181	$45.02	$45.00	$45.00
Purchase #7	$83.81	6.600%	$89.3415	$89.34	$89.35	$89.30
7 purchase totals =	$904.43		$980.7587	$980.76	$980.70	$980.70