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	$161.57	12.533%	$181.8196	$181.82	$181.80	$181.80
Purchase #2	$78.77	5.181%	$82.8511	$82.85	$82.85	$82.90
Purchase #3	$226.47	7.461%	$243.3669	$243.37	$243.35	$243.40
Purchase #4	$133.89	6.667%	$142.8164	$142.82	$142.80	$142.80
Purchase #5	$128.42	12.209%	$144.0988	$144.10	$144.10	$144.10
Purchase #6	$75.90	9.681%	$83.2479	$83.25	$83.25	$83.20
Purchase #7	$240.77	12.273%	$270.3197	$270.32	$270.30	$270.30
7 purchase totals =	$1,045.79		$1,148.5204	$1,148.53	$1,148.45	$1,148.50