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	$123.45	3.283%	$127.5029	$127.50	$127.50	$127.50
Purchase #2	$206.28	8.160%	$223.1124	$223.11	$223.10	$223.10
Purchase #3	$164.71	10.204%	$181.517	$181.52	$181.50	$181.50
Purchase #4	$123.35	4.498%	$128.8983	$128.90	$128.90	$128.90
Purchase #5	$101.98	9.218%	$111.3805	$111.38	$111.40	$111.40
Purchase #6	$119.96	7.485%	$128.939	$128.94	$128.95	$128.90
Purchase #7	$186.61	12.659%	$210.233	$210.23	$210.25	$210.20
7 purchase totals =	$1,026.34		$1,111.5831	$1,111.58	$1,111.60	$1,111.50