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	$99.30	10.574%	$109.8	$109.80	$109.80	$109.80
Purchase #2	$106.44	9.790%	$116.8605	$116.86	$116.85	$116.90
Purchase #3	$246.74	7.587%	$265.4602	$265.46	$265.45	$265.50
Purchase #4	$158.97	7.731%	$171.26	$171.26	$171.25	$171.30
Purchase #5	$166.89	3.585%	$172.873	$172.87	$172.85	$172.90
Purchase #6	$78.64	8.369%	$85.2214	$85.22	$85.20	$85.20
Purchase #7	$204.29	10.323%	$225.3789	$225.38	$225.40	$225.40
7 purchase totals =	$1,061.27		$1,146.8540	$1,146.85	$1,146.80	$1,147.00