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	$83.30	7.302%	$89.3826	$89.38	$89.40	$89.40
Purchase #2	$66.96	6.478%	$71.2977	$71.30	$71.30	$71.30
Purchase #3	$244.77	8.833%	$266.3905	$266.39	$266.40	$266.40
Purchase #4	$101.59	5.326%	$107.0007	$107.00	$107.00	$107.00
Purchase #5	$158.62	8.214%	$171.649	$171.65	$171.65	$171.60
Purchase #6	$169.51	4.383%	$176.9396	$176.94	$176.95	$176.90
Purchase #7	$124.61	7.576%	$134.0505	$134.05	$134.05	$134.10
7 purchase totals =	$949.36		$1,016.7106	$1,016.71	$1,016.75	$1,016.70