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	$85.79	11.381%	$95.5538	$95.55	$95.55	$95.60
Purchase #2	$201.90	5.274%	$212.5482	$212.55	$212.55	$212.50
Purchase #3	$205.68	5.467%	$216.9245	$216.92	$216.90	$216.90
Purchase #4	$180.98	10.810%	$200.5439	$200.54	$200.55	$200.50
Purchase #5	$97.83	11.694%	$109.2702	$109.27	$109.25	$109.30
Purchase #6	$227.74	7.523%	$244.8729	$244.87	$244.85	$244.90
Purchase #7	$182.50	5.311%	$192.1926	$192.19	$192.20	$192.20
7 purchase totals =	$1,182.42		$1,271.9061	$1,271.89	$1,271.85	$1,271.90