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	$49.96	8.559%	$54.2361	$54.24	$54.25	$54.20
Purchase #2	$18.76	7.615%	$20.1886	$20.19	$20.20	$20.20
Purchase #3	$144.54	4.163%	$150.5572	$150.56	$150.55	$150.60
Purchase #4	$125.58	13.676%	$142.7543	$142.75	$142.75	$142.80
Purchase #5	$187.32	6.765%	$199.9922	$199.99	$200.00	$200.00
Purchase #6	$173.98	12.710%	$196.0929	$196.09	$196.10	$196.10
Purchase #7	$51.51	11.854%	$57.616	$57.62	$57.60	$57.60
7 purchase totals =	$751.65		$821.4373	$821.44	$821.45	$821.50