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	$180.90	8.709%	$196.6546	$196.65	$196.65	$196.70
Purchase #2	$102.92	7.836%	$110.9848	$110.98	$111.00	$111.00
Purchase #3	$34.69	4.712%	$36.3246	$36.32	$36.30	$36.30
Purchase #4	$210.62	3.200%	$217.3598	$217.36	$217.35	$217.40
Purchase #5	$168.30	10.703%	$186.3131	$186.31	$186.30	$186.30
Purchase #6	$114.93	7.161%	$123.1601	$123.16	$123.15	$123.20
Purchase #7	$196.57	7.246%	$210.8135	$210.81	$210.80	$210.80
7 purchase totals =	$1,008.93		$1,081.6105	$1,081.59	$1,081.55	$1,081.70