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	$106.91	3.270%	$110.406	$110.41	$110.40	$110.40
Purchase #2	$54.61	7.264%	$58.5769	$58.58	$58.60	$58.60
Purchase #3	$30.45	10.397%	$33.6159	$33.62	$33.60	$33.60
Purchase #4	$177.98	10.657%	$196.9473	$196.95	$196.95	$196.90
Purchase #5	$210.56	5.815%	$222.8041	$222.80	$222.80	$222.80
Purchase #6	$141.70	7.410%	$152.2	$152.20	$152.20	$152.20
Purchase #7	$246.94	8.284%	$267.3965	$267.40	$267.40	$267.40
7 purchase totals =	$969.15		$1,041.9467	$1,041.96	$1,041.95	$1,041.90