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	$219.43	9.814%	$240.9649	$240.96	$240.95	$241.00
Purchase #2	$85.33	10.740%	$94.4944	$94.49	$94.50	$94.50
Purchase #3	$51.59	5.125%	$54.234	$54.23	$54.25	$54.20
Purchase #4	$77.81	6.571%	$82.9229	$82.92	$82.90	$82.90
Purchase #5	$61.37	5.779%	$64.9166	$64.92	$64.90	$64.90
Purchase #6	$54.39	4.851%	$57.0285	$57.03	$57.05	$57.00
Purchase #7	$20.54	10.123%	$22.6193	$22.62	$22.60	$22.60
7 purchase totals =	$570.46		$617.1806	$617.17	$617.15	$617.10