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	$100.62	13.172%	$113.8737	$113.87	$113.85	$113.90
Purchase #2	$229.89	8.850%	$250.2353	$250.24	$250.25	$250.20
Purchase #3	$9.93	13.295%	$11.2502	$11.25	$11.25	$11.30
Purchase #4	$36.50	9.359%	$39.916	$39.92	$39.90	$39.90
Purchase #5	$28.54	10.127%	$31.4302	$31.43	$31.45	$31.40
Purchase #6	$209.70	9.477%	$229.5733	$229.57	$229.55	$229.60
Purchase #7	$51.27	10.641%	$56.7256	$56.73	$56.75	$56.70
7 purchase totals =	$666.45		$733.0043	$733.01	$733.00	$733.00