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	$217.41	11.569%	$242.5622	$242.56	$242.55	$242.60
Purchase #2	$154.43	11.738%	$172.557	$172.56	$172.55	$172.60
Purchase #3	$181.46	6.338%	$192.9609	$192.96	$192.95	$193.00
Purchase #4	$82.25	8.294%	$89.0718	$89.07	$89.05	$89.10
Purchase #5	$213.68	9.342%	$233.642	$233.64	$233.65	$233.60
Purchase #6	$89.35	10.603%	$98.8238	$98.82	$98.80	$98.80
Purchase #7	$128.52	9.670%	$140.9479	$140.95	$140.95	$140.90
7 purchase totals =	$1,067.10		$1,170.5656	$1,170.56	$1,170.50	$1,170.60