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	$200.76	3.311%	$207.4072	$207.41	$207.40	$207.40
Purchase #2	$95.85	7.757%	$103.2851	$103.29	$103.30	$103.30
Purchase #3	$119.46	3.779%	$123.9744	$123.97	$123.95	$124.00
Purchase #4	$221.25	7.696%	$238.2774	$238.28	$238.30	$238.30
Purchase #5	$154.93	13.524%	$175.8827	$175.88	$175.90	$175.90
Purchase #6	$160.54	3.156%	$165.6066	$165.61	$165.60	$165.60
Purchase #7	$78.82	10.404%	$87.0204	$87.02	$87.00	$87.00
7 purchase totals =	$1,031.61		$1,101.4538	$1,101.46	$1,101.45	$1,101.50