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	$227.65	3.271%	$235.0964	$235.10	$235.10	$235.10
Purchase #2	$93.48	10.731%	$103.5113	$103.51	$103.50	$103.50
Purchase #3	$27.87	6.165%	$29.5882	$29.59	$29.60	$29.60
Purchase #4	$93.90	9.592%	$102.9069	$102.91	$102.90	$102.90
Purchase #5	$68.30	7.556%	$73.4607	$73.46	$73.45	$73.50
Purchase #6	$54.39	9.792%	$59.7159	$59.72	$59.70	$59.70
Purchase #7	$138.48	7.310%	$148.6029	$148.60	$148.60	$148.60
7 purchase totals =	$704.07		$752.8823	$752.89	$752.85	$752.90