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	$152.73	5.307%	$160.8354	$160.84	$160.85	$160.80
Purchase #2	$248.35	10.322%	$273.9847	$273.98	$274.00	$274.00
Purchase #3	$183.76	3.585%	$190.3478	$190.35	$190.35	$190.30
Purchase #4	$110.46	9.335%	$120.7714	$120.77	$120.75	$120.80
Purchase #5	$51.63	10.351%	$56.9742	$56.97	$56.95	$57.00
Purchase #6	$98.40	11.656%	$109.8695	$109.87	$109.85	$109.90
Purchase #7	$95.67	5.122%	$100.5702	$100.57	$100.55	$100.60
7 purchase totals =	$941.00		$1,013.3532	$1,013.35	$1,013.30	$1,013.40