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	$116.91	8.594%	$126.9572	$126.96	$126.95	$127.00
Purchase #2	$125.62	4.506%	$131.2804	$131.28	$131.30	$131.30
Purchase #3	$19.46	3.638%	$20.168	$20.17	$20.15	$20.20
Purchase #4	$29.61	10.689%	$32.775	$32.78	$32.80	$32.80
Purchase #5	$158.79	6.358%	$168.8859	$168.89	$168.90	$168.90
Purchase #6	$209.38	6.593%	$223.1844	$223.18	$223.20	$223.20
Purchase #7	$250.59	9.548%	$274.5163	$274.52	$274.50	$274.50
7 purchase totals =	$910.36		$977.7672	$977.78	$977.80	$977.90