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	$205.31	3.428%	$212.348	$212.35	$212.35	$212.30
Purchase #2	$136.70	3.649%	$141.6882	$141.69	$141.70	$141.70
Purchase #3	$63.74	6.368%	$67.799	$67.80	$67.80	$67.80
Purchase #4	$80.48	10.768%	$89.1461	$89.15	$89.15	$89.10
Purchase #5	$77.41	11.533%	$86.3377	$86.34	$86.35	$86.30
Purchase #6	$159.58	5.677%	$168.6394	$168.64	$168.65	$168.60
Purchase #7	$127.42	4.237%	$132.8188	$132.82	$132.80	$132.80
7 purchase totals =	$850.64		$898.7772	$898.79	$898.80	$898.60