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	$208.61	11.137%	$231.8429	$231.84	$231.85	$231.80
Purchase #2	$150.44	3.615%	$155.8784	$155.88	$155.90	$155.90
Purchase #3	$58.48	5.822%	$61.8847	$61.88	$61.90	$61.90
Purchase #4	$67.61	13.585%	$76.7948	$76.79	$76.80	$76.80
Purchase #5	$38.35	12.539%	$43.1587	$43.16	$43.15	$43.20
Purchase #6	$213.94	6.541%	$227.9338	$227.93	$227.95	$227.90
Purchase #7	$62.74	13.739%	$71.3598	$71.36	$71.35	$71.40
7 purchase totals =	$800.17		$868.8531	$868.84	$868.90	$868.90