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	$83.47	7.548%	$89.7703	$89.77	$89.75	$89.80
Purchase #2	$201.88	3.324%	$208.5905	$208.59	$208.60	$208.60
Purchase #3	$192.72	7.270%	$206.7307	$206.73	$206.75	$206.70
Purchase #4	$191.41	12.793%	$215.8971	$215.90	$215.90	$215.90
Purchase #5	$106.35	9.378%	$116.3235	$116.32	$116.30	$116.30
Purchase #6	$138.31	12.323%	$155.3539	$155.35	$155.35	$155.40
Purchase #7	$134.52	3.864%	$139.7179	$139.72	$139.70	$139.70
7 purchase totals =	$1,048.66		$1,132.3839	$1,132.38	$1,132.35	$1,132.40