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	$70.58	10.727%	$78.1511	$78.15	$78.15	$78.20
Purchase #2	$196.55	5.853%	$208.0541	$208.05	$208.05	$208.10
Purchase #3	$92.82	10.164%	$102.2542	$102.25	$102.25	$102.30
Purchase #4	$101.57	12.480%	$114.2459	$114.25	$114.25	$114.20
Purchase #5	$240.48	5.373%	$253.401	$253.40	$253.40	$253.40
Purchase #6	$62.42	11.329%	$69.4916	$69.49	$69.50	$69.50
Purchase #7	$105.76	9.839%	$116.1657	$116.17	$116.15	$116.20
7 purchase totals =	$870.18		$941.7636	$941.76	$941.75	$941.90