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	$105.93	7.488%	$113.862	$113.86	$113.85	$113.90
Purchase #2	$76.63	13.828%	$87.2264	$87.23	$87.25	$87.20
Purchase #3	$131.52	8.548%	$142.7623	$142.76	$142.75	$142.80
Purchase #4	$88.40	4.286%	$92.1888	$92.19	$92.20	$92.20
Purchase #5	$124.51	13.397%	$141.1906	$141.19	$141.20	$141.20
Purchase #6	$25.59	7.138%	$27.4166	$27.42	$27.40	$27.40
Purchase #7	$136.82	3.653%	$141.818	$141.82	$141.80	$141.80
7 purchase totals =	$689.40		$746.4647	$746.47	$746.45	$746.50