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	$74.61	11.166%	$82.941	$82.94	$82.95	$82.90
Purchase #2	$69.52	12.258%	$78.0418	$78.04	$78.05	$78.00
Purchase #3	$124.76	13.296%	$141.3481	$141.35	$141.35	$141.30
Purchase #4	$206.53	8.658%	$224.4114	$224.41	$224.40	$224.40
Purchase #5	$9.84	3.209%	$10.1558	$10.16	$10.15	$10.20
Purchase #6	$242.25	6.562%	$258.1464	$258.15	$258.15	$258.10
Purchase #7	$151.46	8.618%	$164.5128	$164.51	$164.50	$164.50
7 purchase totals =	$878.97		$959.5573	$959.56	$959.55	$959.40