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	$197.30	8.410%	$213.8929	$213.89	$213.90	$213.90
Purchase #2	$93.99	7.855%	$101.3729	$101.37	$101.35	$101.40
Purchase #3	$65.26	11.170%	$72.5495	$72.55	$72.55	$72.50
Purchase #4	$107.90	4.611%	$112.8753	$112.88	$112.90	$112.90
Purchase #5	$35.76	3.442%	$36.9909	$36.99	$37.00	$37.00
Purchase #6	$123.64	13.164%	$139.916	$139.92	$139.90	$139.90
Purchase #7	$55.51	5.454%	$58.5375	$58.54	$58.55	$58.50
7 purchase totals =	$679.36		$736.1350	$736.14	$736.15	$736.10