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	$167.93	12.851%	$189.5107	$189.51	$189.50	$189.50
Purchase #2	$41.69	6.442%	$44.3757	$44.38	$44.40	$44.40
Purchase #3	$200.99	6.290%	$213.6323	$213.63	$213.65	$213.60
Purchase #4	$114.69	5.226%	$120.6837	$120.68	$120.70	$120.70
Purchase #5	$216.25	6.108%	$229.4586	$229.46	$229.45	$229.50
Purchase #6	$238.30	7.482%	$256.1296	$256.13	$256.15	$256.10
Purchase #7	$29.38	10.430%	$32.4443	$32.44	$32.45	$32.40
7 purchase totals =	$1,009.23		$1,086.2349	$1,086.23	$1,086.30	$1,086.20