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	$113.65	5.111%	$119.4587	$119.46	$119.45	$119.50
Purchase #2	$216.29	9.745%	$237.3675	$237.37	$237.35	$237.40
Purchase #3	$28.32	4.112%	$29.4845	$29.48	$29.50	$29.50
Purchase #4	$22.44	12.686%	$25.2867	$25.29	$25.30	$25.30
Purchase #5	$225.37	7.619%	$242.5409	$242.54	$242.55	$242.50
Purchase #6	$109.69	5.256%	$115.4553	$115.46	$115.45	$115.50
Purchase #7	$80.56	11.265%	$89.6351	$89.64	$89.65	$89.60
7 purchase totals =	$796.32		$859.2287	$859.24	$859.25	$859.30