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	$50.56	7.661%	$54.4334	$54.43	$54.45	$54.40
Purchase #2	$205.89	4.428%	$215.0068	$215.01	$215.00	$215.00
Purchase #3	$85.59	6.294%	$90.977	$90.98	$91.00	$91.00
Purchase #4	$95.85	13.544%	$108.8319	$108.83	$108.85	$108.80
Purchase #5	$216.40	9.750%	$237.499	$237.50	$237.50	$237.50
Purchase #6	$112.41	13.596%	$127.6933	$127.69	$127.70	$127.70
Purchase #7	$186.55	9.838%	$204.9028	$204.90	$204.90	$204.90
7 purchase totals =	$953.25		$1,039.3442	$1,039.34	$1,039.40	$1,039.30