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	$145.57	5.751%	$153.9417	$153.94	$153.95	$153.90
Purchase #2	$18.86	12.630%	$21.242	$21.24	$21.25	$21.20
Purchase #3	$72.40	6.822%	$77.3391	$77.34	$77.35	$77.30
Purchase #4	$111.29	8.525%	$120.7775	$120.78	$120.80	$120.80
Purchase #5	$143.49	4.571%	$150.0489	$150.05	$150.05	$150.00
Purchase #6	$167.96	12.281%	$188.5872	$188.59	$188.60	$188.60
Purchase #7	$104.64	12.311%	$117.5222	$117.52	$117.50	$117.50
7 purchase totals =	$764.21		$829.4586	$829.46	$829.50	$829.30