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	$57.39	3.788%	$59.5639	$59.56	$59.55	$59.60
Purchase #2	$34.45	8.551%	$37.3958	$37.40	$37.40	$37.40
Purchase #3	$97.67	12.470%	$109.8494	$109.85	$109.85	$109.80
Purchase #4	$228.61	7.730%	$246.2816	$246.28	$246.30	$246.30
Purchase #5	$132.72	3.175%	$136.9339	$136.93	$136.95	$136.90
Purchase #6	$236.75	11.569%	$264.1396	$264.14	$264.15	$264.10
Purchase #7	$57.83	8.657%	$62.8363	$62.84	$62.85	$62.80
7 purchase totals =	$845.42		$917.0005	$917.00	$917.05	$916.90