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	$185.97	3.270%	$192.0512	$192.05	$192.05	$192.10
Purchase #2	$132.96	6.438%	$141.52	$141.52	$141.50	$141.50
Purchase #3	$84.34	9.398%	$92.2663	$92.27	$92.25	$92.30
Purchase #4	$121.48	4.556%	$127.0146	$127.01	$127.00	$127.00
Purchase #5	$231.42	9.519%	$253.4489	$253.45	$253.45	$253.40
Purchase #6	$131.73	8.658%	$143.1352	$143.14	$143.15	$143.10
Purchase #7	$123.98	10.260%	$136.7003	$136.70	$136.70	$136.70
7 purchase totals =	$1,011.88		$1,086.1365	$1,086.14	$1,086.10	$1,086.10