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	$34.76	9.725%	$38.1404	$38.14	$38.15	$38.10
Purchase #2	$145.59	4.516%	$152.1648	$152.16	$152.15	$152.20
Purchase #3	$223.99	9.587%	$245.4639	$245.46	$245.45	$245.50
Purchase #4	$218.81	6.459%	$232.9429	$232.94	$232.95	$232.90
Purchase #5	$182.86	6.402%	$194.5667	$194.57	$194.55	$194.60
Purchase #6	$124.66	3.167%	$128.608	$128.61	$128.60	$128.60
Purchase #7	$64.94	10.835%	$71.9762	$71.98	$72.00	$72.00
7 purchase totals =	$995.61		$1,063.8629	$1,063.86	$1,063.85	$1,063.90