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	$102.64	8.740%	$111.6107	$111.61	$111.60	$111.60
Purchase #2	$219.49	6.103%	$232.8855	$232.89	$232.90	$232.90
Purchase #3	$42.38	6.732%	$45.233	$45.23	$45.25	$45.20
Purchase #4	$39.54	8.663%	$42.9654	$42.97	$42.95	$43.00
Purchase #5	$190.68	12.660%	$214.8201	$214.82	$214.80	$214.80
Purchase #6	$100.72	8.554%	$109.3356	$109.34	$109.35	$109.30
Purchase #7	$86.35	9.592%	$94.6327	$94.63	$94.65	$94.60
7 purchase totals =	$781.80		$851.4830	$851.49	$851.50	$851.40