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	$40.49	8.275%	$43.8405	$43.84	$43.85	$43.80
Purchase #2	$180.67	11.192%	$200.8906	$200.89	$200.90	$200.90
Purchase #3	$130.52	9.183%	$142.5057	$142.51	$142.50	$142.50
Purchase #4	$232.99	11.366%	$259.4716	$259.47	$259.45	$259.50
Purchase #5	$142.98	6.280%	$151.9591	$151.96	$151.95	$152.00
Purchase #6	$156.72	3.773%	$162.633	$162.63	$162.65	$162.60
Purchase #7	$42.60	6.204%	$45.2429	$45.24	$45.25	$45.20
7 purchase totals =	$926.97		$1,006.5434	$1,006.54	$1,006.55	$1,006.50