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	$228.27	6.380%	$242.8336	$242.83	$242.85	$242.80
Purchase #2	$237.50	6.602%	$253.1798	$253.18	$253.20	$253.20
Purchase #3	$205.41	3.753%	$213.119	$213.12	$213.10	$213.10
Purchase #4	$232.40	7.156%	$249.0305	$249.03	$249.05	$249.00
Purchase #5	$71.46	10.119%	$78.691	$78.69	$78.70	$78.70
Purchase #6	$41.94	13.477%	$47.5923	$47.59	$47.60	$47.60
Purchase #7	$166.82	3.296%	$172.3184	$172.32	$172.30	$172.30
7 purchase totals =	$1,183.80		$1,256.7646	$1,256.76	$1,256.80	$1,256.70