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	$184.74	13.329%	$209.364	$209.36	$209.35	$209.40
Purchase #2	$197.37	13.464%	$223.9439	$223.94	$223.95	$223.90
Purchase #3	$59.81	13.559%	$67.9196	$67.92	$67.90	$67.90
Purchase #4	$183.63	7.207%	$196.8642	$196.86	$196.85	$196.90
Purchase #5	$104.30	13.638%	$118.5244	$118.52	$118.50	$118.50
Purchase #6	$50.85	5.134%	$53.4606	$53.46	$53.45	$53.50
Purchase #7	$221.27	3.768%	$229.6075	$229.61	$229.60	$229.60
7 purchase totals =	$1,001.97		$1,099.6842	$1,099.67	$1,099.60	$1,099.70