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	$59.45	3.166%	$61.3322	$61.33	$61.35	$61.30
Purchase #2	$25.62	10.414%	$28.2881	$28.29	$28.30	$28.30
Purchase #3	$21.77	11.666%	$24.3097	$24.31	$24.30	$24.30
Purchase #4	$76.66	12.265%	$86.0623	$86.06	$86.05	$86.10
Purchase #5	$152.31	5.428%	$160.5774	$160.58	$160.60	$160.60
Purchase #6	$164.96	6.720%	$176.0453	$176.05	$176.05	$176.00
Purchase #7	$22.83	6.812%	$24.3852	$24.39	$24.40	$24.40
7 purchase totals =	$523.60		$561.0002	$561.01	$561.05	$561.00