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	$187.30	9.821%	$205.6947	$205.69	$205.70	$205.70
Purchase #2	$97.64	11.680%	$109.0444	$109.04	$109.05	$109.00
Purchase #3	$215.51	11.275%	$239.8088	$239.81	$239.80	$239.80
Purchase #4	$20.63	9.530%	$22.596	$22.60	$22.60	$22.60
Purchase #5	$244.98	10.426%	$270.5216	$270.52	$270.50	$270.50
Purchase #6	$40.56	5.745%	$42.8902	$42.89	$42.90	$42.90
Purchase #7	$241.43	4.207%	$251.587	$251.59	$251.60	$251.60
7 purchase totals =	$1,048.05		$1,142.1427	$1,142.14	$1,142.15	$1,142.10