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	$125.41	6.653%	$133.7535	$133.75	$133.75	$133.80
Purchase #2	$91.94	4.290%	$95.8842	$95.88	$95.90	$95.90
Purchase #3	$195.88	10.217%	$215.8931	$215.89	$215.90	$215.90
Purchase #4	$159.80	4.525%	$167.031	$167.03	$167.05	$167.00
Purchase #5	$147.90	7.233%	$158.5976	$158.60	$158.60	$158.60
Purchase #6	$73.57	12.757%	$82.9553	$82.96	$82.95	$83.00
Purchase #7	$236.90	8.837%	$257.8349	$257.83	$257.85	$257.80
7 purchase totals =	$1,031.40		$1,111.9496	$1,111.94	$1,112.00	$1,112.00