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	$235.92	5.391%	$248.6384	$248.64	$248.65	$248.60
Purchase #2	$40.82	6.752%	$43.5762	$43.58	$43.60	$43.60
Purchase #3	$144.85	4.494%	$151.3596	$151.36	$151.35	$151.40
Purchase #4	$121.46	11.566%	$135.5081	$135.51	$135.50	$135.50
Purchase #5	$174.98	12.531%	$196.9067	$196.91	$196.90	$196.90
Purchase #6	$176.69	5.457%	$186.332	$186.33	$186.35	$186.30
Purchase #7	$33.50	6.408%	$35.6467	$35.65	$35.65	$35.60
7 purchase totals =	$928.22		$997.9677	$997.98	$998.00	$997.90