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	$210.96	10.841%	$233.8302	$233.83	$233.85	$233.80
Purchase #2	$231.39	4.416%	$241.6082	$241.61	$241.60	$241.60
Purchase #3	$51.98	10.686%	$57.5346	$57.53	$57.55	$57.50
Purchase #4	$185.39	4.760%	$194.2146	$194.21	$194.20	$194.20
Purchase #5	$129.50	5.692%	$136.8711	$136.87	$136.85	$136.90
Purchase #6	$166.67	13.678%	$189.4671	$189.47	$189.45	$189.50
Purchase #7	$133.44	6.799%	$142.5126	$142.51	$142.50	$142.50
7 purchase totals =	$1,109.33		$1,196.0384	$1,196.03	$1,196.00	$1,196.00