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	$224.80	5.335%	$236.7931	$236.79	$236.80	$236.80
Purchase #2	$166.98	10.796%	$185.0072	$185.01	$185.00	$185.00
Purchase #3	$153.28	12.786%	$172.8784	$172.88	$172.90	$172.90
Purchase #4	$223.73	6.108%	$237.3954	$237.40	$237.40	$237.40
Purchase #5	$36.42	9.558%	$39.901	$39.90	$39.90	$39.90
Purchase #6	$36.89	9.350%	$40.3392	$40.34	$40.35	$40.30
Purchase #7	$185.51	7.775%	$199.9334	$199.93	$199.95	$199.90
7 purchase totals =	$1,027.61		$1,112.2477	$1,112.25	$1,112.30	$1,112.20