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	$212.37	8.108%	$229.589	$229.59	$229.60	$229.60
Purchase #2	$240.37	7.451%	$258.28	$258.28	$258.30	$258.30
Purchase #3	$232.57	6.556%	$247.8173	$247.82	$247.80	$247.80
Purchase #4	$80.86	11.672%	$90.298	$90.30	$90.30	$90.30
Purchase #5	$250.29	11.220%	$278.3725	$278.37	$278.35	$278.40
Purchase #6	$203.57	9.119%	$222.1335	$222.13	$222.15	$222.10
Purchase #7	$221.80	7.292%	$237.9737	$237.97	$237.95	$238.00
7 purchase totals =	$1,441.83		$1,564.4640	$1,564.46	$1,564.45	$1,564.50