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	$237.59	7.280%	$254.8866	$254.89	$254.90	$254.90
Purchase #2	$171.25	9.364%	$187.2859	$187.29	$187.30	$187.30
Purchase #3	$203.70	3.719%	$211.2756	$211.28	$211.30	$211.30
Purchase #4	$148.45	5.499%	$156.6133	$156.61	$156.60	$156.60
Purchase #5	$71.33	3.196%	$73.6097	$73.61	$73.60	$73.60
Purchase #6	$21.96	8.842%	$23.9017	$23.90	$23.90	$23.90
Purchase #7	$123.72	13.112%	$139.9422	$139.94	$139.95	$139.90
7 purchase totals =	$978.00		$1,047.5150	$1,047.52	$1,047.55	$1,047.50