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	$197.46	9.331%	$215.885	$215.89	$215.90	$215.90
Purchase #2	$143.63	6.654%	$153.1871	$153.19	$153.20	$153.20
Purchase #3	$53.63	5.634%	$56.6515	$56.65	$56.65	$56.70
Purchase #4	$126.71	3.670%	$131.3603	$131.36	$131.35	$131.40
Purchase #5	$172.92	8.647%	$187.8724	$187.87	$187.85	$187.90
Purchase #6	$231.37	13.159%	$261.816	$261.82	$261.80	$261.80
Purchase #7	$85.89	9.435%	$93.9937	$93.99	$94.00	$94.00
7 purchase totals =	$1,011.61		$1,100.7660	$1,100.77	$1,100.75	$1,100.90