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	$146.79	10.726%	$162.5347	$162.53	$162.55	$162.50
Purchase #2	$48.29	6.395%	$51.3781	$51.38	$51.40	$51.40
Purchase #3	$82.86	3.685%	$85.9134	$85.91	$85.90	$85.90
Purchase #4	$245.26	8.765%	$266.757	$266.76	$266.75	$266.80
Purchase #5	$116.67	9.589%	$127.8575	$127.86	$127.85	$127.90
Purchase #6	$70.76	4.197%	$73.7298	$73.73	$73.75	$73.70
Purchase #7	$161.86	6.712%	$172.724	$172.72	$172.70	$172.70
7 purchase totals =	$872.49		$940.8945	$940.89	$940.90	$940.90