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	$89.41	10.131%	$98.4681	$98.47	$98.45	$98.50
Purchase #2	$38.30	13.647%	$43.5268	$43.53	$43.55	$43.50
Purchase #3	$206.97	9.153%	$225.914	$225.91	$225.90	$225.90
Purchase #4	$53.66	10.734%	$59.4199	$59.42	$59.40	$59.40
Purchase #5	$120.63	5.355%	$127.0897	$127.09	$127.10	$127.10
Purchase #6	$157.51	6.548%	$167.8238	$167.82	$167.80	$167.80
Purchase #7	$157.67	6.402%	$167.764	$167.76	$167.75	$167.80
7 purchase totals =	$824.15		$890.0063	$890.00	$889.95	$890.00