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	$93.36	7.803%	$100.6449	$100.64	$100.65	$100.60
Purchase #2	$136.62	10.129%	$150.4582	$150.46	$150.45	$150.50
Purchase #3	$196.90	3.680%	$204.1459	$204.15	$204.15	$204.10
Purchase #4	$245.61	3.830%	$255.0169	$255.02	$255.00	$255.00
Purchase #5	$164.51	4.252%	$171.505	$171.51	$171.50	$171.50
Purchase #6	$153.53	12.380%	$172.537	$172.54	$172.55	$172.50
Purchase #7	$132.33	6.741%	$141.2504	$141.25	$141.25	$141.30
7 purchase totals =	$1,122.86		$1,195.5583	$1,195.57	$1,195.55	$1,195.50