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	$77.59	3.470%	$80.2824	$80.28	$80.30	$80.30
Purchase #2	$210.83	5.785%	$223.0265	$223.03	$223.05	$223.00
Purchase #3	$211.67	12.390%	$237.8959	$237.90	$237.90	$237.90
Purchase #4	$127.42	10.379%	$140.6449	$140.64	$140.65	$140.60
Purchase #5	$52.95	12.567%	$59.6042	$59.60	$59.60	$59.60
Purchase #6	$64.89	12.409%	$72.9422	$72.94	$72.95	$72.90
Purchase #7	$208.35	4.479%	$217.682	$217.68	$217.70	$217.70
7 purchase totals =	$953.70		$1,032.0781	$1,032.07	$1,032.15	$1,032.00