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	$61.71	9.843%	$67.7841	$67.78	$67.80	$67.80
Purchase #2	$99.67	8.192%	$107.835	$107.84	$107.85	$107.80
Purchase #3	$6.78	10.419%	$7.4864	$7.49	$7.50	$7.50
Purchase #4	$97.46	7.782%	$105.0443	$105.04	$105.05	$105.00
Purchase #5	$78.71	13.632%	$89.4397	$89.44	$89.45	$89.40
Purchase #6	$20.31	7.170%	$21.7662	$21.77	$21.75	$21.80
Purchase #7	$201.67	11.118%	$224.0917	$224.09	$224.10	$224.10
7 purchase totals =	$566.31		$623.4474	$623.45	$623.50	$623.40