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	$66.62	11.816%	$74.4918	$74.49	$74.50	$74.50
Purchase #2	$235.46	11.578%	$262.7216	$262.72	$262.70	$262.70
Purchase #3	$196.43	7.662%	$211.4805	$211.48	$211.50	$211.50
Purchase #4	$154.53	8.124%	$167.084	$167.08	$167.10	$167.10
Purchase #5	$82.72	3.453%	$85.5763	$85.58	$85.60	$85.60
Purchase #6	$29.84	9.504%	$32.676	$32.68	$32.70	$32.70
Purchase #7	$202.61	9.814%	$222.4941	$222.49	$222.50	$222.50
7 purchase totals =	$968.21		$1,056.5243	$1,056.52	$1,056.60	$1,056.60