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	$136.82	11.606%	$152.6993	$152.70	$152.70	$152.70
Purchase #2	$133.93	6.565%	$142.7225	$142.72	$142.70	$142.70
Purchase #3	$203.38	3.704%	$210.9132	$210.91	$210.90	$210.90
Purchase #4	$115.53	6.827%	$123.4172	$123.42	$123.40	$123.40
Purchase #5	$12.40	10.163%	$13.6602	$13.66	$13.65	$13.70
Purchase #6	$137.74	4.755%	$144.2895	$144.29	$144.30	$144.30
Purchase #7	$93.79	6.436%	$99.8263	$99.83	$99.85	$99.80
7 purchase totals =	$833.59		$887.5282	$887.53	$887.50	$887.50