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	$151.37	13.271%	$171.4583	$171.46	$171.45	$171.50
Purchase #2	$69.73	9.704%	$76.4966	$76.50	$76.50	$76.50
Purchase #3	$171.98	13.618%	$195.4002	$195.40	$195.40	$195.40
Purchase #4	$149.58	7.650%	$161.0229	$161.02	$161.00	$161.00
Purchase #5	$213.53	6.365%	$227.1212	$227.12	$227.10	$227.10
Purchase #6	$212.25	12.358%	$238.4799	$238.48	$238.50	$238.50
Purchase #7	$118.93	6.415%	$126.5594	$126.56	$126.55	$126.60
7 purchase totals =	$1,087.37		$1,196.5385	$1,196.54	$1,196.50	$1,196.60