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	$111.75	3.243%	$115.3741	$115.37	$115.35	$115.40
Purchase #2	$99.60	3.169%	$102.7563	$102.76	$102.75	$102.80
Purchase #3	$14.28	10.626%	$15.7974	$15.80	$15.80	$15.80
Purchase #4	$136.25	6.514%	$145.1253	$145.13	$145.15	$145.10
Purchase #5	$119.47	9.781%	$131.1554	$131.16	$131.15	$131.20
Purchase #6	$141.61	10.744%	$156.8246	$156.82	$156.80	$156.80
Purchase #7	$147.53	11.520%	$164.5255	$164.53	$164.55	$164.50
7 purchase totals =	$770.49		$831.5586	$831.57	$831.55	$831.60