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	$120.73	10.134%	$132.9648	$132.96	$132.95	$133.00
Purchase #2	$78.81	3.222%	$81.3493	$81.35	$81.35	$81.30
Purchase #3	$168.46	13.248%	$190.7776	$190.78	$190.80	$190.80
Purchase #4	$239.87	3.715%	$248.7812	$248.78	$248.80	$248.80
Purchase #5	$69.89	9.281%	$76.3765	$76.38	$76.40	$76.40
Purchase #6	$165.69	12.237%	$185.9655	$185.97	$185.95	$186.00
Purchase #7	$84.59	12.376%	$95.0589	$95.06	$95.05	$95.10
7 purchase totals =	$928.04		$1,011.2738	$1,011.28	$1,011.30	$1,011.40