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	$67.42	8.150%	$72.9147	$72.91	$72.90	$72.90
Purchase #2	$14.50	9.153%	$15.8272	$15.83	$15.85	$15.80
Purchase #3	$135.94	4.738%	$142.3808	$142.38	$142.40	$142.40
Purchase #4	$43.44	13.836%	$49.4504	$49.45	$49.45	$49.50
Purchase #5	$219.44	11.317%	$244.274	$244.27	$244.25	$244.30
Purchase #6	$202.29	6.851%	$216.1489	$216.15	$216.15	$216.10
Purchase #7	$100.26	10.673%	$110.9607	$110.96	$110.95	$111.00
7 purchase totals =	$783.29		$851.9567	$851.95	$851.95	$852.00