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	$236.50	4.431%	$246.9793	$246.98	$247.00	$247.00
Purchase #2	$128.41	6.788%	$137.1265	$137.13	$137.15	$137.10
Purchase #3	$85.48	4.651%	$89.4557	$89.46	$89.45	$89.50
Purchase #4	$126.37	13.127%	$142.9586	$142.96	$142.95	$143.00
Purchase #5	$145.33	8.368%	$157.4912	$157.49	$157.50	$157.50
Purchase #6	$53.46	8.712%	$58.1174	$58.12	$58.10	$58.10
Purchase #7	$91.67	11.644%	$102.3441	$102.34	$102.35	$102.30
7 purchase totals =	$867.22		$934.4728	$934.48	$934.50	$934.50