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	$225.45	11.184%	$250.6643	$250.66	$250.65	$250.70
Purchase #2	$59.93	12.626%	$67.4968	$67.50	$67.50	$67.50
Purchase #3	$242.28	8.223%	$262.2027	$262.20	$262.20	$262.20
Purchase #4	$166.53	7.177%	$178.4819	$178.48	$178.50	$178.50
Purchase #5	$145.98	3.124%	$150.5404	$150.54	$150.55	$150.50
Purchase #6	$119.72	13.294%	$135.6356	$135.64	$135.65	$135.60
Purchase #7	$240.43	10.435%	$265.5189	$265.52	$265.50	$265.50
7 purchase totals =	$1,200.32		$1,310.5406	$1,310.54	$1,310.55	$1,310.50