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	$179.48	9.709%	$196.9057	$196.91	$196.90	$196.90
Purchase #2	$213.88	3.615%	$221.6118	$221.61	$221.60	$221.60
Purchase #3	$232.38	12.667%	$261.8156	$261.82	$261.80	$261.80
Purchase #4	$219.27	3.696%	$227.3742	$227.37	$227.35	$227.40
Purchase #5	$93.68	8.667%	$101.7992	$101.80	$101.80	$101.80
Purchase #6	$83.93	5.467%	$88.5185	$88.52	$88.50	$88.50
Purchase #7	$56.69	9.160%	$61.8828	$61.88	$61.90	$61.90
7 purchase totals =	$1,079.31		$1,159.9078	$1,159.91	$1,159.85	$1,159.90