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	$114.43	11.591%	$127.6936	$127.69	$127.70	$127.70
Purchase #2	$165.95	7.759%	$178.8261	$178.83	$178.85	$178.80
Purchase #3	$187.46	4.608%	$196.0982	$196.10	$196.10	$196.10
Purchase #4	$124.46	8.832%	$135.4523	$135.45	$135.45	$135.50
Purchase #5	$30.76	3.211%	$31.7477	$31.75	$31.75	$31.70
Purchase #6	$89.56	9.367%	$97.9491	$97.95	$97.95	$97.90
Purchase #7	$112.89	5.681%	$119.3033	$119.30	$119.30	$119.30
7 purchase totals =	$825.51		$887.0703	$887.07	$887.10	$887.00