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	$36.85	13.527%	$41.8347	$41.83	$41.85	$41.80
Purchase #2	$59.71	13.819%	$67.9613	$67.96	$67.95	$68.00
Purchase #3	$213.48	5.780%	$225.8191	$225.82	$225.80	$225.80
Purchase #4	$119.82	4.584%	$125.3125	$125.31	$125.30	$125.30
Purchase #5	$105.43	10.164%	$116.1459	$116.15	$116.15	$116.10
Purchase #6	$89.48	6.391%	$95.1987	$95.20	$95.20	$95.20
Purchase #7	$66.84	3.727%	$69.3311	$69.33	$69.35	$69.30
7 purchase totals =	$691.61		$741.6033	$741.60	$741.60	$741.50