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	$150.60	12.108%	$168.8346	$168.83	$168.85	$168.80
Purchase #2	$67.76	7.693%	$72.9728	$72.97	$72.95	$73.00
Purchase #3	$182.55	9.300%	$199.5272	$199.53	$199.55	$199.50
Purchase #4	$48.97	6.710%	$52.2559	$52.26	$52.25	$52.30
Purchase #5	$101.93	7.436%	$109.5095	$109.51	$109.50	$109.50
Purchase #6	$86.25	3.743%	$89.4783	$89.48	$89.50	$89.50
Purchase #7	$110.49	13.543%	$125.4537	$125.45	$125.45	$125.50
7 purchase totals =	$748.55		$818.0320	$818.03	$818.05	$818.10