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	$221.92	9.791%	$243.6482	$243.65	$243.65	$243.60
Purchase #2	$135.32	4.710%	$141.6936	$141.69	$141.70	$141.70
Purchase #3	$178.52	10.150%	$196.6398	$196.64	$196.65	$196.60
Purchase #4	$71.62	9.367%	$78.3286	$78.33	$78.35	$78.30
Purchase #5	$36.70	9.523%	$40.1949	$40.19	$40.20	$40.20
Purchase #6	$6.85	3.298%	$7.0759	$7.08	$7.10	$7.10
Purchase #7	$71.64	12.699%	$80.7376	$80.74	$80.75	$80.70
7 purchase totals =	$722.57		$788.3186	$788.32	$788.40	$788.20