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	$153.44	10.207%	$169.1016	$169.10	$169.10	$169.10
Purchase #2	$174.91	6.855%	$186.9001	$186.90	$186.90	$186.90
Purchase #3	$22.76	8.742%	$24.7497	$24.75	$24.75	$24.70
Purchase #4	$89.75	8.632%	$97.4972	$97.50	$97.50	$97.50
Purchase #5	$232.81	12.237%	$261.299	$261.30	$261.30	$261.30
Purchase #6	$211.26	5.785%	$223.4814	$223.48	$223.50	$223.50
Purchase #7	$108.75	13.870%	$123.8336	$123.83	$123.85	$123.80
7 purchase totals =	$993.68		$1,086.8626	$1,086.86	$1,086.90	$1,086.80