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	$60.30	8.596%	$65.4834	$65.48	$65.50	$65.50
Purchase #2	$232.57	7.672%	$250.4128	$250.41	$250.40	$250.40
Purchase #3	$246.25	11.185%	$273.7931	$273.79	$273.80	$273.80
Purchase #4	$94.59	9.503%	$103.5789	$103.58	$103.60	$103.60
Purchase #5	$194.94	6.853%	$208.2992	$208.30	$208.30	$208.30
Purchase #6	$229.30	5.770%	$242.5306	$242.53	$242.55	$242.50
Purchase #7	$203.98	9.726%	$223.8191	$223.82	$223.80	$223.80
7 purchase totals =	$1,261.93		$1,367.9171	$1,367.91	$1,367.95	$1,367.90