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	$69.31	10.574%	$76.6388	$76.64	$76.65	$76.60
Purchase #2	$136.71	10.159%	$150.5984	$150.60	$150.60	$150.60
Purchase #3	$130.58	10.207%	$143.9083	$143.91	$143.90	$143.90
Purchase #4	$132.51	7.613%	$142.598	$142.60	$142.60	$142.60
Purchase #5	$224.99	11.257%	$250.3171	$250.32	$250.30	$250.30
Purchase #6	$55.84	11.319%	$62.1605	$62.16	$62.15	$62.20
Purchase #7	$181.47	13.436%	$205.8523	$205.85	$205.85	$205.90
7 purchase totals =	$931.41		$1,032.0734	$1,032.08	$1,032.05	$1,032.10