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	$238.87	9.457%	$261.4599	$261.46	$261.45	$261.50
Purchase #2	$131.75	7.466%	$141.5865	$141.59	$141.60	$141.60
Purchase #3	$98.32	10.316%	$108.4627	$108.46	$108.45	$108.50
Purchase #4	$203.93	3.813%	$211.7059	$211.71	$211.70	$211.70
Purchase #5	$97.61	4.848%	$102.3421	$102.34	$102.35	$102.30
Purchase #6	$35.79	7.640%	$38.5244	$38.52	$38.50	$38.50
Purchase #7	$99.95	4.374%	$104.3218	$104.32	$104.30	$104.30
7 purchase totals =	$906.22		$968.4033	$968.40	$968.35	$968.40