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	$142.83	6.315%	$151.8497	$151.85	$151.85	$151.80
Purchase #2	$153.87	9.812%	$168.9677	$168.97	$168.95	$169.00
Purchase #3	$63.94	4.806%	$67.013	$67.01	$67.00	$67.00
Purchase #4	$127.43	3.154%	$131.4491	$131.45	$131.45	$131.40
Purchase #5	$61.62	10.574%	$68.1357	$68.14	$68.15	$68.10
Purchase #6	$88.67	3.142%	$91.456	$91.46	$91.45	$91.50
Purchase #7	$179.52	4.662%	$187.8892	$187.89	$187.90	$187.90
7 purchase totals =	$817.88		$866.7604	$866.77	$866.75	$866.70