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	$83.26	4.357%	$86.8876	$86.89	$86.90	$86.90
Purchase #2	$52.89	12.536%	$59.5203	$59.52	$59.50	$59.50
Purchase #3	$108.71	9.839%	$119.406	$119.41	$119.40	$119.40
Purchase #4	$234.96	10.649%	$259.9809	$259.98	$260.00	$260.00
Purchase #5	$130.27	8.572%	$141.4367	$141.44	$141.45	$141.40
Purchase #6	$132.85	13.645%	$150.9774	$150.98	$151.00	$151.00
Purchase #7	$171.50	13.165%	$194.078	$194.08	$194.10	$194.10
7 purchase totals =	$914.44		$1,012.2869	$1,012.30	$1,012.35	$1,012.30