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	$58.37	5.630%	$61.6562	$61.66	$61.65	$61.70
Purchase #2	$21.96	12.443%	$24.6925	$24.69	$24.70	$24.70
Purchase #3	$136.35	3.203%	$140.7173	$140.72	$140.70	$140.70
Purchase #4	$19.32	7.417%	$20.753	$20.75	$20.75	$20.80
Purchase #5	$53.38	11.134%	$59.3233	$59.32	$59.30	$59.30
Purchase #6	$140.83	5.803%	$149.0024	$149.00	$149.00	$149.00
Purchase #7	$235.32	13.629%	$267.3918	$267.39	$267.40	$267.40
7 purchase totals =	$665.53		$723.5365	$723.53	$723.50	$723.60