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	$71.91	9.497%	$78.7393	$78.74	$78.75	$78.70
Purchase #2	$207.41	6.458%	$220.8045	$220.80	$220.80	$220.80
Purchase #3	$35.85	8.267%	$38.8137	$38.81	$38.80	$38.80
Purchase #4	$200.67	13.278%	$227.315	$227.32	$227.30	$227.30
Purchase #5	$69.36	13.460%	$78.6959	$78.70	$78.70	$78.70
Purchase #6	$47.82	6.276%	$50.8212	$50.82	$50.80	$50.80
Purchase #7	$56.62	4.752%	$59.3106	$59.31	$59.30	$59.30
7 purchase totals =	$689.64		$754.5002	$754.50	$754.45	$754.40