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	$158.99	13.789%	$180.9131	$180.91	$180.90	$180.90
Purchase #2	$68.50	11.660%	$76.4871	$76.49	$76.50	$76.50
Purchase #3	$174.42	12.691%	$196.5556	$196.56	$196.55	$196.60
Purchase #4	$223.82	3.645%	$231.9782	$231.98	$232.00	$232.00
Purchase #5	$216.53	10.497%	$239.2592	$239.26	$239.25	$239.30
Purchase #6	$185.85	5.609%	$196.2743	$196.27	$196.25	$196.30
Purchase #7	$243.89	11.693%	$272.4081	$272.41	$272.40	$272.40
7 purchase totals =	$1,272.00		$1,393.8756	$1,393.88	$1,393.85	$1,394.00