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	$144.62	13.779%	$164.5472	$164.55	$164.55	$164.50
Purchase #2	$140.69	11.325%	$156.6231	$156.62	$156.60	$156.60
Purchase #3	$76.73	13.132%	$86.8062	$86.81	$86.80	$86.80
Purchase #4	$6.64	6.867%	$7.096	$7.10	$7.10	$7.10
Purchase #5	$211.63	10.387%	$233.612	$233.61	$233.60	$233.60
Purchase #6	$69.35	10.411%	$76.57	$76.57	$76.55	$76.60
Purchase #7	$80.83	10.267%	$89.1288	$89.13	$89.15	$89.10
7 purchase totals =	$730.49		$814.3833	$814.39	$814.35	$814.30