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	$199.71	5.309%	$210.3126	$210.31	$210.30	$210.30
Purchase #2	$152.28	13.137%	$172.285	$172.29	$172.30	$172.30
Purchase #3	$194.69	3.199%	$200.9181	$200.92	$200.90	$200.90
Purchase #4	$206.76	9.838%	$227.101	$227.10	$227.10	$227.10
Purchase #5	$99.45	13.340%	$112.7166	$112.72	$112.70	$112.70
Purchase #6	$87.48	12.406%	$98.3328	$98.33	$98.35	$98.30
Purchase #7	$131.50	7.867%	$141.8451	$141.85	$141.85	$141.80
7 purchase totals =	$1,071.87		$1,163.5112	$1,163.52	$1,163.50	$1,163.40