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	$131.71	11.366%	$146.6802	$146.68	$146.70	$146.70
Purchase #2	$103.80	5.870%	$109.8931	$109.89	$109.90	$109.90
Purchase #3	$127.35	9.745%	$139.7603	$139.76	$139.75	$139.80
Purchase #4	$70.91	13.520%	$80.497	$80.50	$80.50	$80.50
Purchase #5	$31.28	11.401%	$34.8462	$34.85	$34.85	$34.80
Purchase #6	$89.40	11.332%	$99.5308	$99.53	$99.55	$99.50
Purchase #7	$77.69	7.391%	$83.4321	$83.43	$83.45	$83.40
7 purchase totals =	$632.14		$694.6397	$694.64	$694.70	$694.60