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	$193.64	4.238%	$201.8465	$201.85	$201.85	$201.80
Purchase #2	$230.36	12.657%	$259.5167	$259.52	$259.50	$259.50
Purchase #3	$126.65	13.810%	$144.1404	$144.14	$144.15	$144.10
Purchase #4	$54.92	8.431%	$59.5503	$59.55	$59.55	$59.60
Purchase #5	$215.49	13.214%	$243.9648	$243.96	$243.95	$244.00
Purchase #6	$118.73	7.722%	$127.8983	$127.90	$127.90	$127.90
Purchase #7	$98.56	4.483%	$102.9784	$102.98	$103.00	$103.00
7 purchase totals =	$1,038.35		$1,139.8954	$1,139.90	$1,139.90	$1,139.90