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	$225.35	10.714%	$249.494	$249.49	$249.50	$249.50
Purchase #2	$25.92	6.840%	$27.6929	$27.69	$27.70	$27.70
Purchase #3	$172.63	6.618%	$184.0547	$184.05	$184.05	$184.10
Purchase #4	$179.48	9.412%	$196.3727	$196.37	$196.35	$196.40
Purchase #5	$163.87	9.832%	$179.9817	$179.98	$180.00	$180.00
Purchase #6	$200.72	11.476%	$223.7546	$223.75	$223.75	$223.80
Purchase #7	$128.89	11.134%	$143.2406	$143.24	$143.25	$143.20
7 purchase totals =	$1,096.86		$1,204.5912	$1,204.57	$1,204.60	$1,204.70