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	$199.50	11.350%	$222.1433	$222.14	$222.15	$222.10
Purchase #2	$238.94	3.235%	$246.6697	$246.67	$246.65	$246.70
Purchase #3	$78.92	8.330%	$85.494	$85.49	$85.50	$85.50
Purchase #4	$46.75	6.215%	$49.6555	$49.66	$49.65	$49.70
Purchase #5	$32.55	3.788%	$33.783	$33.78	$33.80	$33.80
Purchase #6	$69.58	3.799%	$72.2233	$72.22	$72.20	$72.20
Purchase #7	$25.25	8.787%	$27.4687	$27.47	$27.45	$27.50
7 purchase totals =	$691.49		$737.4375	$737.43	$737.40	$737.50