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	$137.54	13.799%	$156.5191	$156.52	$156.50	$156.50
Purchase #2	$208.36	9.675%	$228.5188	$228.52	$228.50	$228.50
Purchase #3	$123.78	6.223%	$131.4828	$131.48	$131.50	$131.50
Purchase #4	$128.36	11.866%	$143.5912	$143.59	$143.60	$143.60
Purchase #5	$184.34	6.133%	$195.6456	$195.65	$195.65	$195.60
Purchase #6	$115.44	12.789%	$130.2036	$130.20	$130.20	$130.20
Purchase #7	$182.76	7.782%	$196.9824	$196.98	$197.00	$197.00
7 purchase totals =	$1,080.58		$1,182.9435	$1,182.94	$1,182.95	$1,182.90