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	$83.25	13.530%	$94.5137	$94.51	$94.50	$94.50
Purchase #2	$77.82	12.322%	$87.409	$87.41	$87.40	$87.40
Purchase #3	$162.87	12.256%	$182.8313	$182.83	$182.85	$182.80
Purchase #4	$122.34	4.528%	$127.8796	$127.88	$127.90	$127.90
Purchase #5	$244.90	12.324%	$275.0815	$275.08	$275.10	$275.10
Purchase #6	$89.98	5.608%	$95.0261	$95.03	$95.05	$95.00
Purchase #7	$206.50	7.698%	$222.3964	$222.40	$222.40	$222.40
7 purchase totals =	$987.66		$1,085.1376	$1,085.14	$1,085.20	$1,085.10