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	$242.76	4.565%	$253.842	$253.84	$253.85	$253.80
Purchase #2	$114.39	7.391%	$122.8446	$122.84	$122.85	$122.80
Purchase #3	$209.98	7.331%	$225.3736	$225.37	$225.35	$225.40
Purchase #4	$64.32	12.228%	$72.185	$72.19	$72.20	$72.20
Purchase #5	$5.77	12.399%	$6.4854	$6.49	$6.50	$6.50
Purchase #6	$215.69	10.563%	$238.4733	$238.47	$238.45	$238.50
Purchase #7	$130.95	10.475%	$144.667	$144.67	$144.65	$144.70
7 purchase totals =	$983.86		$1,063.8709	$1,063.87	$1,063.85	$1,063.90