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	$126.97	10.538%	$140.3501	$140.35	$140.35	$140.40
Purchase #2	$214.59	10.303%	$236.6992	$236.70	$236.70	$236.70
Purchase #3	$69.73	11.221%	$77.5544	$77.55	$77.55	$77.60
Purchase #4	$200.31	5.149%	$210.624	$210.62	$210.60	$210.60
Purchase #5	$89.79	11.860%	$100.4391	$100.44	$100.45	$100.40
Purchase #6	$243.90	9.632%	$267.3924	$267.39	$267.40	$267.40
Purchase #7	$102.60	8.597%	$111.4205	$111.42	$111.40	$111.40
7 purchase totals =	$1,047.89		$1,144.4797	$1,144.47	$1,144.45	$1,144.50