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	$73.74	10.267%	$81.3109	$81.31	$81.30	$81.30
Purchase #2	$193.46	9.379%	$211.6046	$211.60	$211.60	$211.60
Purchase #3	$152.65	9.333%	$166.8968	$166.90	$166.90	$166.90
Purchase #4	$93.88	12.314%	$105.4404	$105.44	$105.45	$105.40
Purchase #5	$113.73	12.553%	$128.0065	$128.01	$128.00	$128.00
Purchase #6	$194.47	13.563%	$220.846	$220.85	$220.85	$220.80
Purchase #7	$151.96	3.647%	$157.502	$157.50	$157.50	$157.50
7 purchase totals =	$973.89		$1,071.6072	$1,071.61	$1,071.60	$1,071.50