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	$62.62	4.185%	$65.2406	$65.24	$65.25	$65.20
Purchase #2	$223.62	6.504%	$238.1642	$238.16	$238.15	$238.20
Purchase #3	$23.67	5.112%	$24.88	$24.88	$24.90	$24.90
Purchase #4	$29.63	13.224%	$33.5483	$33.55	$33.55	$33.50
Purchase #5	$193.68	7.710%	$208.6127	$208.61	$208.60	$208.60
Purchase #6	$226.30	13.328%	$256.4613	$256.46	$256.45	$256.50
Purchase #7	$187.82	4.727%	$196.6983	$196.70	$196.70	$196.70
7 purchase totals =	$947.34		$1,023.6054	$1,023.60	$1,023.60	$1,023.60