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	$187.67	4.835%	$196.7438	$196.74	$196.75	$196.70
Purchase #2	$140.64	12.829%	$158.6827	$158.68	$158.70	$158.70
Purchase #3	$25.87	11.643%	$28.882	$28.88	$28.90	$28.90
Purchase #4	$67.34	8.414%	$73.006	$73.01	$73.00	$73.00
Purchase #5	$108.36	9.420%	$118.5675	$118.57	$118.55	$118.60
Purchase #6	$208.40	12.137%	$233.6935	$233.69	$233.70	$233.70
Purchase #7	$248.43	5.574%	$262.2775	$262.28	$262.30	$262.30
7 purchase totals =	$986.71		$1,071.8530	$1,071.85	$1,071.90	$1,071.90