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	$206.47	3.554%	$213.8079	$213.81	$213.80	$213.80
Purchase #2	$195.63	4.317%	$204.0753	$204.08	$204.10	$204.10
Purchase #3	$89.58	9.744%	$98.3087	$98.31	$98.30	$98.30
Purchase #4	$128.93	12.860%	$145.5104	$145.51	$145.50	$145.50
Purchase #5	$91.47	4.828%	$95.8862	$95.89	$95.90	$95.90
Purchase #6	$31.58	9.574%	$34.6035	$34.60	$34.60	$34.60
Purchase #7	$212.88	4.651%	$222.781	$222.78	$222.80	$222.80
7 purchase totals =	$956.54		$1,014.9730	$1,014.98	$1,015.00	$1,015.00