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	$128.43	13.599%	$145.8952	$145.90	$145.90	$145.90
Purchase #2	$5.46	8.405%	$5.9189	$5.92	$5.90	$5.90
Purchase #3	$79.58	9.611%	$87.2284	$87.23	$87.25	$87.20
Purchase #4	$85.56	4.650%	$89.5385	$89.54	$89.55	$89.50
Purchase #5	$49.68	10.714%	$55.0027	$55.00	$55.00	$55.00
Purchase #6	$41.50	8.191%	$44.8993	$44.90	$44.90	$44.90
Purchase #7	$185.30	7.852%	$199.8498	$199.85	$199.85	$199.80
7 purchase totals =	$575.51		$628.3328	$628.34	$628.35	$628.20