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	$147.47	10.320%	$162.6889	$162.69	$162.70	$162.70
Purchase #2	$105.63	3.625%	$109.4591	$109.46	$109.45	$109.50
Purchase #3	$119.77	13.827%	$136.3306	$136.33	$136.35	$136.30
Purchase #4	$234.90	7.382%	$252.2403	$252.24	$252.25	$252.20
Purchase #5	$190.63	7.735%	$205.3752	$205.38	$205.40	$205.40
Purchase #6	$113.61	8.397%	$123.1498	$123.15	$123.15	$123.10
Purchase #7	$109.92	8.665%	$119.4446	$119.44	$119.45	$119.40
7 purchase totals =	$1,021.93		$1,108.6885	$1,108.69	$1,108.75	$1,108.60