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	$105.34	11.628%	$117.5889	$117.59	$117.60	$117.60
Purchase #2	$109.41	9.553%	$119.8619	$119.86	$119.85	$119.90
Purchase #3	$95.64	5.746%	$101.1355	$101.14	$101.15	$101.10
Purchase #4	$223.78	10.360%	$246.9636	$246.96	$246.95	$247.00
Purchase #5	$31.47	6.819%	$33.6159	$33.62	$33.60	$33.60
Purchase #6	$217.69	9.386%	$238.1224	$238.12	$238.10	$238.10
Purchase #7	$145.46	9.668%	$159.5231	$159.52	$159.50	$159.50
7 purchase totals =	$928.79		$1,016.8113	$1,016.81	$1,016.75	$1,016.80