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	$164.69	4.186%	$171.5839	$171.58	$171.60	$171.60
Purchase #2	$72.89	13.567%	$82.779	$82.78	$82.80	$82.80
Purchase #3	$247.41	13.503%	$280.8178	$280.82	$280.80	$280.80
Purchase #4	$157.98	11.716%	$176.4889	$176.49	$176.50	$176.50
Purchase #5	$217.42	8.553%	$236.0159	$236.02	$236.00	$236.00
Purchase #6	$33.76	5.560%	$35.6371	$35.64	$35.65	$35.60
Purchase #7	$199.71	3.571%	$206.8416	$206.84	$206.85	$206.80
7 purchase totals =	$1,093.86		$1,190.1642	$1,190.17	$1,190.20	$1,190.10