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	$236.93	6.426%	$252.1551	$252.16	$252.15	$252.20
Purchase #2	$116.45	10.154%	$128.2743	$128.27	$128.25	$128.30
Purchase #3	$98.47	5.316%	$103.7047	$103.70	$103.70	$103.70
Purchase #4	$127.31	10.138%	$140.2167	$140.22	$140.20	$140.20
Purchase #5	$142.76	5.295%	$150.3191	$150.32	$150.30	$150.30
Purchase #6	$177.89	7.803%	$191.7708	$191.77	$191.75	$191.80
Purchase #7	$66.47	7.704%	$71.5908	$71.59	$71.60	$71.60
7 purchase totals =	$966.28		$1,038.0315	$1,038.03	$1,037.95	$1,038.10