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	$130.38	4.664%	$136.4609	$136.46	$136.45	$136.50
Purchase #2	$134.59	3.668%	$139.5268	$139.53	$139.55	$139.50
Purchase #3	$198.47	5.648%	$209.6796	$209.68	$209.70	$209.70
Purchase #4	$186.59	8.563%	$202.5677	$202.57	$202.55	$202.60
Purchase #5	$80.31	12.160%	$90.0757	$90.08	$90.10	$90.10
Purchase #6	$196.29	7.409%	$210.8331	$210.83	$210.85	$210.80
Purchase #7	$190.99	3.109%	$196.9279	$196.93	$196.95	$196.90
7 purchase totals =	$1,117.62		$1,186.0717	$1,186.08	$1,186.15	$1,186.10