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	$85.94	4.269%	$89.6088	$89.61	$89.60	$89.60
Purchase #2	$240.57	11.387%	$267.9637	$267.96	$267.95	$268.00
Purchase #3	$156.81	12.786%	$176.8597	$176.86	$176.85	$176.90
Purchase #4	$113.40	5.603%	$119.7538	$119.75	$119.75	$119.80
Purchase #5	$32.92	12.841%	$37.1473	$37.15	$37.15	$37.10
Purchase #6	$194.62	11.461%	$216.9254	$216.93	$216.95	$216.90
Purchase #7	$195.75	10.654%	$216.6052	$216.61	$216.60	$216.60
7 purchase totals =	$1,020.01		$1,124.8639	$1,124.87	$1,124.85	$1,124.90