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	$198.56	6.546%	$211.5577	$211.56	$211.55	$211.60
Purchase #2	$241.50	3.732%	$250.5128	$250.51	$250.50	$250.50
Purchase #3	$86.88	10.772%	$96.2387	$96.24	$96.25	$96.20
Purchase #4	$84.54	11.404%	$94.1809	$94.18	$94.20	$94.20
Purchase #5	$205.94	13.184%	$233.0911	$233.09	$233.10	$233.10
Purchase #6	$128.62	13.491%	$145.9721	$145.97	$145.95	$146.00
Purchase #7	$59.51	3.669%	$61.6934	$61.69	$61.70	$61.70
7 purchase totals =	$1,005.55		$1,093.2467	$1,093.24	$1,093.25	$1,093.30