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	$123.31	6.599%	$131.4472	$131.45	$131.45	$131.40
Purchase #2	$167.50	8.271%	$181.3539	$181.35	$181.35	$181.40
Purchase #3	$59.59	13.436%	$67.5965	$67.60	$67.60	$67.60
Purchase #4	$133.88	4.555%	$139.9782	$139.98	$140.00	$140.00
Purchase #5	$59.52	9.137%	$64.9583	$64.96	$64.95	$65.00
Purchase #6	$225.64	13.786%	$256.7467	$256.75	$256.75	$256.70
Purchase #7	$195.99	7.350%	$210.3953	$210.40	$210.40	$210.40
7 purchase totals =	$965.43		$1,052.4761	$1,052.49	$1,052.50	$1,052.50