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	$75.56	4.503%	$78.9625	$78.96	$78.95	$79.00
Purchase #2	$177.77	5.113%	$186.8594	$186.86	$186.85	$186.90
Purchase #3	$55.25	6.743%	$58.9755	$58.98	$59.00	$59.00
Purchase #4	$47.97	8.302%	$51.9525	$51.95	$51.95	$52.00
Purchase #5	$90.85	11.837%	$101.6039	$101.60	$101.60	$101.60
Purchase #6	$163.33	8.634%	$177.4319	$177.43	$177.45	$177.40
Purchase #7	$99.91	5.554%	$105.459	$105.46	$105.45	$105.50
7 purchase totals =	$710.64		$761.2447	$761.24	$761.25	$761.40