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	$245.29	4.215%	$255.629	$255.63	$255.65	$255.60
Purchase #2	$134.36	8.412%	$145.6624	$145.66	$145.65	$145.70
Purchase #3	$116.54	5.534%	$122.9893	$122.99	$123.00	$123.00
Purchase #4	$85.87	4.330%	$89.5882	$89.59	$89.60	$89.60
Purchase #5	$156.84	10.260%	$172.9318	$172.93	$172.95	$172.90
Purchase #6	$157.93	13.272%	$178.8905	$178.89	$178.90	$178.90
Purchase #7	$198.71	8.567%	$215.7335	$215.73	$215.75	$215.70
7 purchase totals =	$1,095.54		$1,181.4247	$1,181.42	$1,181.50	$1,181.40