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	$105.48	10.809%	$116.8813	$116.88	$116.90	$116.90
Purchase #2	$104.85	13.542%	$119.0488	$119.05	$119.05	$119.00
Purchase #3	$82.78	8.406%	$89.7385	$89.74	$89.75	$89.70
Purchase #4	$184.49	11.298%	$205.3337	$205.33	$205.35	$205.30
Purchase #5	$118.66	9.547%	$129.9885	$129.99	$130.00	$130.00
Purchase #6	$38.36	10.353%	$42.3314	$42.33	$42.35	$42.30
Purchase #7	$196.73	7.547%	$211.5772	$211.58	$211.60	$211.60
7 purchase totals =	$831.35		$914.8994	$914.90	$915.00	$914.80