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	$92.77	13.144%	$104.9637	$104.96	$104.95	$105.00
Purchase #2	$92.83	10.288%	$102.3804	$102.38	$102.40	$102.40
Purchase #3	$76.49	5.546%	$80.7321	$80.73	$80.75	$80.70
Purchase #4	$239.59	4.103%	$249.4204	$249.42	$249.40	$249.40
Purchase #5	$83.43	7.158%	$89.4019	$89.40	$89.40	$89.40
Purchase #6	$29.94	4.732%	$31.3568	$31.36	$31.35	$31.40
Purchase #7	$177.92	7.482%	$191.232	$191.23	$191.25	$191.20
7 purchase totals =	$792.97		$849.4873	$849.48	$849.50	$849.50