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	$24.86	4.125%	$25.8855	$25.89	$25.90	$25.90
Purchase #2	$157.39	6.496%	$167.6141	$167.61	$167.60	$167.60
Purchase #3	$97.74	6.434%	$104.0286	$104.03	$104.05	$104.00
Purchase #4	$16.55	11.289%	$18.4183	$18.42	$18.40	$18.40
Purchase #5	$81.59	9.146%	$89.0522	$89.05	$89.05	$89.10
Purchase #6	$61.86	4.113%	$64.4043	$64.40	$64.40	$64.40
Purchase #7	$30.33	6.713%	$32.3661	$32.37	$32.35	$32.40
7 purchase totals =	$470.32		$501.7691	$501.77	$501.75	$501.80