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	$240.54	12.124%	$269.7031	$269.70	$269.70	$269.70
Purchase #2	$133.86	12.321%	$150.3529	$150.35	$150.35	$150.40
Purchase #3	$115.86	13.691%	$131.7224	$131.72	$131.70	$131.70
Purchase #4	$81.57	9.595%	$89.3966	$89.40	$89.40	$89.40
Purchase #5	$123.31	8.389%	$133.6545	$133.65	$133.65	$133.70
Purchase #6	$155.68	13.668%	$176.9583	$176.96	$176.95	$177.00
Purchase #7	$67.64	6.487%	$72.0278	$72.03	$72.05	$72.00
7 purchase totals =	$918.46		$1,023.8156	$1,023.81	$1,023.80	$1,023.90